diff --git a/.dependabot/config.yml b/.dependabot/config.yml
index a3bd09e6..2d68a999 100644
--- a/.dependabot/config.yml
+++ b/.dependabot/config.yml
@@ -3,7 +3,13 @@
 version: 1
 
 update_configs:
-  - default_assignees:
+  - automerged_updates:
+      - match:
+          dependency_type: "development"
+    commit_message:
+      include_scope: true
+      prefix: "Build"
+    default_assignees:
       - "localheinz"
     default_labels:
       - "dependency"
diff --git a/.gitattributes b/.gitattributes
index 7d7a5306..36d16720 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -1,10 +1,13 @@
-/.dependabot/       export-ignore
-/.github/           export-ignore
-/test/              export-ignore
-/.editorconfig      export-ignore
-/.gitattributes     export-ignore
-/.gitignore         export-ignore
-/.php_cs            export-ignore
-/infection.json     export-ignore
-/Makefile           export-ignore
-/phpstan.neon       export-ignore
+/.dependabot/           export-ignore
+/.github/               export-ignore
+/test/                  export-ignore
+/.editorconfig          export-ignore
+/.gitattributes         export-ignore
+/.gitignore             export-ignore
+/.php_cs                export-ignore
+/infection.json         export-ignore
+/Makefile               export-ignore
+/phpstan-baseline.neon  export-ignore
+/phpstan.neon           export-ignore
+/psalm-baseline.xml     export-ignore
+/psalm.xml              export-ignore
diff --git a/.github/CONTRIBUTING.md b/.github/CONTRIBUTING.md
index ceddbcd7..285ab618 100644
--- a/.github/CONTRIBUTING.md
+++ b/.github/CONTRIBUTING.md
@@ -30,7 +30,7 @@ to run a dependency analysis.
 
 ## Static Code Analysis
 
-We are using [`phpstan/phpstan`](https://github.com/phpstan/phpstan) to statically analyze the code.
+We are using [`phpstan/phpstan`](https://github.com/phpstan/phpstan) and [`vimeo/psalm`](https://github.com/vimeo/psalm) to statically analyze the code.
 
 Run
 
@@ -40,7 +40,7 @@ $ make static-code-analysis
 
 to run a static code analysis.
 
-We are also using the [baseline feature](https://medium.com/@ondrejmirtes/phpstans-baseline-feature-lets-you-hold-new-code-to-a-higher-standard-e77d815a5dff) of [`phpstan/phpstan`](https://github.com/phpstan/phpstan).
+We are also using the baseline features of [`phpstan/phpstan`(https://medium.com/@ondrejmirtes/phpstans-baseline-feature-lets-you-hold-new-code-to-a-higher-standard-e77d815a5dff) and [`vimeo/psalm`](https://psalm.dev/docs/running_psalm/dealing_with_code_issues/#using-a-baseline-file).
 
 Run
 
@@ -48,9 +48,9 @@ Run
 $ make static-code-analysis-baseline
 ```
 
-to regenerate the baseline in [`../phpstan-baseline.neon`](../phpstan-baseline.neon).
+to regenerate the baselines in [`../phpstan-baseline.neon`](../phpstan-baseline.neon) and [`../psalm-baseline.xml`](../psalm-baseline.xml).
 
-:exclamation: Ideally, the baseline should shrink over time.
+:exclamation: Ideally, the baselines should shrink over time.
 
 ## Tests
 
diff --git a/.github/settings.yml b/.github/settings.yml
index 0b690670..59733b4b 100644
--- a/.github/settings.yml
+++ b/.github/settings.yml
@@ -1,7 +1,11 @@
 # https://github.com/probot/settings
 
 branches:
-  - name: master
+  - name: "master"
+
+    # https://developer.github.com/v3/repos/branches/#remove-branch-protection
+    # https://developer.github.com/v3/repos/branches/#update-branch-protection
+
     protection:
       enforce_admins: false
       required_pull_request_reviews:
@@ -30,26 +34,41 @@ branches:
           - "codecov/patch"
           - "codecov/project"
         strict: false
-      restrictions: null
+      restrictions:
+        apps:
+          - "dependabot-preview"
+        teams: []
+        users: []
+
+# https://developer.github.com/v3/issues/labels/#create-a-label
+# https://developer.github.com/v3/issues/labels/#update-a-label
 
 labels:
-  - name: bug
-    color: ee0701
+  - name: "bug"
+    color: "#ee0701"
+    description: ""
 
-  - name: dependency
-    color: 0366d6
+  - name: "dependency"
+    color: "#0366d6"
+    description: ""
 
-  - name: enhancement
-    color: 0e8a16
+  - name: "enhancement"
+    color: "#0e8a16"
+    description: ""
 
-  - name: question
-    color: cc317c
+  - name: "question"
+    color: "#cc317c"
+    description: ""
 
-  - name: security
-    color: ee0701
+  - name: "security"
+    color: "#ee0701"
+    description: ""
 
-  - name: stale
-    color: eeeeee
+  - name: "stale"
+    color: "#eeeeee"
+    description: ""
+
+# https://developer.github.com/v3/repos/#edit
 
 repository:
   allow_merge_commit: true
@@ -62,5 +81,9 @@ repository:
   has_pages: false
   has_projects: false
   has_wiki: false
-  name: php-cs-fixer-config
+  name: "php-cs-fixer-config"
   private: false
+
+  # https://developer.github.com/v3/repos/branches/#remove-branch-protection
+
+  topics: "php-cs-fixer, configuration"
diff --git a/.github/workflows/approve.yml b/.github/workflows/approve.yml
new file mode 100644
index 00000000..cb33191e
--- /dev/null
+++ b/.github/workflows/approve.yml
@@ -0,0 +1,19 @@
+# https://help.github.com/en/categories/automating-your-workflow-with-github-actions
+
+name: "Approve"
+
+on:
+  - "pull_request"
+
+jobs:
+  approve:
+    name: "Approve"
+
+    runs-on: "ubuntu-latest"
+
+    steps:
+      - name: "Approve"
+        uses: "hmarr/auto-approve-action@v2.0.0"
+        if: "(github.actor == 'dependabot[bot]' || github.actor == 'dependabot-preview[bot]') && startsWith(github.event.pull_request.title, 'Build(deps-dev)')"
+        with:
+          github-token: "${{ secrets.GITHUB_TOKEN }}"
diff --git a/.github/workflows/continuous-deployment.yml b/.github/workflows/continuous-deployment.yml
new file mode 100644
index 00000000..b91f7d58
--- /dev/null
+++ b/.github/workflows/continuous-deployment.yml
@@ -0,0 +1,29 @@
+# https://help.github.com/en/categories/automating-your-workflow-with-github-actions
+
+name: "Continuous Deployment"
+
+on:
+  push:
+    tags:
+      - "**"
+
+jobs:
+  release:
+    name: "Release"
+
+    runs-on: "ubuntu-latest"
+
+    steps:
+      - name: "Determine tag"
+        id: "determine-tag"
+        run: "echo \"::set-output name=tag::${GITHUB_REF#refs/tags/}\""
+
+      - name: "Create release"
+        uses: "actions/create-release@v1.0.0"
+        env:
+          GITHUB_TOKEN: "${{ secrets.GITHUB_TOKEN }}"
+        with:
+          draft: false
+          prerelease: false
+          release_name: "${{ steps.determine-tag.outputs.tag }}"
+          tag_name: "${{ steps.determine-tag.outputs.tag }}"
diff --git a/.github/workflows/continuous-integration.yml b/.github/workflows/continuous-integration.yml
index ad6a2d9c..ab3ca7ba 100644
--- a/.github/workflows/continuous-integration.yml
+++ b/.github/workflows/continuous-integration.yml
@@ -1,285 +1,335 @@
 # https://help.github.com/en/categories/automating-your-workflow-with-github-actions
 
+name: "Continuous Integration"
+
 on:
   pull_request:
   push:
     branches:
-      - master
-    tags:
-      - "**"
+      - "master"
 
-name: "Continuous Integration"
+env:
+  MIN_COVERED_MSI: 100
+  MIN_MSI: 100
+  REQUIRED_PHP_EXTENSIONS: "mbstring"
 
 jobs:
   coding-standards:
     name: "Coding Standards"
 
-    runs-on: ubuntu-latest
+    runs-on: "ubuntu-latest"
 
     strategy:
       matrix:
         php-version:
-          - 7.1
+          - "7.1"
 
         dependencies:
-          - locked
+          - "locked"
 
     steps:
       - name: "Checkout"
-        uses: actions/checkout@v2.0.0
+        uses: "actions/checkout@v2.0.0"
 
       - name: "Install PHP with extensions"
-        uses: shivammathur/setup-php@1.6.1
+        uses: "shivammathur/setup-php@1.7.0"
         with:
-          coverage: none
-          extensions: "mbstring"
-          php-version: ${{ matrix.php-version }}
+          coverage: "none"
+          extensions: "${{ env.REQUIRED_PHP_EXTENSIONS }}"
+          php-version: "${{ matrix.php-version }}"
 
       - name: "Validate composer.json and composer.lock"
-        run: composer validate --strict
+        run: "composer validate --strict"
 
       - name: "Cache dependencies installed with composer"
-        uses: actions/cache@v1.0.3
+        uses: "actions/cache@v1.0.3"
         with:
-          path: ~/.composer/cache
-          key: php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-${{ hashFiles('**/composer.lock') }}
-          restore-keys: |
-            php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-
+          path: "~/.composer/cache"
+          key: "php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-${{ hashFiles('**/composer.lock') }}"
+          restore-keys: "php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-"
+
+      - name: "Install lowest dependencies with composer"
+        if: "matrix.dependencies == 'lowest'"
+        run: "composer update --no-interaction --no-progress --no-suggest --prefer-lowest"
 
       - name: "Install locked dependencies with composer"
-        run: composer install --no-interaction --no-progress --no-suggest
+        if: "matrix.dependencies == 'locked'"
+        run: "composer install --no-interaction --no-progress --no-suggest"
+
+      - name: "Install highest dependencies with composer"
+        if: "matrix.dependencies == 'highest'"
+        run: "composer update --no-interaction --no-progress --no-suggest"
 
       - name: "Run ergebnis/composer-normalize"
-        run: composer normalize --dry-run
+        run: "composer normalize --dry-run"
 
       - name: "Create cache directory for friendsofphp/php-cs-fixer"
-        run: mkdir -p .build/php-cs-fixer
+        run: "mkdir -p .build/php-cs-fixer"
 
       - name: "Cache cache directory for friendsofphp/php-cs-fixer"
-        uses: actions/cache@v1.0.3
+        uses: "actions/cache@v1.0.3"
         with:
-          path: .build/php-cs-fixer
-          key: php-${{ matrix.php-version }}-php-cs-fixer-${{ hashFiles('**/composer.lock') }}
-          restore-keys: |
-            php-${{ matrix.php-version }}-php-cs-fixer-
+          path: ".build/php-cs-fixer"
+          key: "php-${{ matrix.php-version }}-php-cs-fixer-${{ hashFiles('**/composer.lock') }}"
+          restore-keys: "php-${{ matrix.php-version }}-php-cs-fixer-"
 
       - name: "Run friendsofphp/php-cs-fixer"
-        run: vendor/bin/php-cs-fixer fix --config=.php_cs --diff --diff-format=udiff --dry-run --verbose
+        run: "vendor/bin/php-cs-fixer fix --config=.php_cs --diff --diff-format=udiff --dry-run --verbose"
 
   dependency-analysis:
     name: "Dependency Analysis"
 
-    runs-on: ubuntu-latest
+    runs-on: "ubuntu-latest"
 
     strategy:
       matrix:
         php-version:
-          - 7.4
+          - "7.4"
 
         dependencies:
-          - locked
+          - "locked"
 
     steps:
       - name: "Checkout"
-        uses: actions/checkout@v2.0.0
+        uses: "actions/checkout@v2.0.0"
 
       - name: "Install PHP with extensions"
-        uses: shivammathur/setup-php@1.6.1
+        uses: "shivammathur/setup-php@1.7.0"
         with:
-          coverage: none
-          extensions: "mbstring"
-          php-version: ${{ matrix.php-version }}
+          coverage: "none"
+          extensions: "${{ env.REQUIRED_PHP_EXTENSIONS }}"
+          php-version: "${{ matrix.php-version }}"
 
       - name: "Cache dependencies installed with composer"
-        uses: actions/cache@v1.0.3
+        uses: "actions/cache@v1.0.3"
         with:
-          path: ~/.composer/cache
-          key: php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-${{ hashFiles('**/composer.lock') }}
-          restore-keys: |
-            php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-
+          path: "~/.composer/cache"
+          key: "php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-${{ hashFiles('**/composer.lock') }}"
+          restore-keys: "php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-"
+
+      - name: "Install lowest dependencies with composer"
+        if: "matrix.dependencies == 'lowest'"
+        run: "composer update --no-interaction --no-progress --no-suggest --prefer-lowest"
 
       - name: "Install locked dependencies with composer"
-        run: composer install --no-interaction --no-progress --no-suggest
+        if: "matrix.dependencies == 'locked'"
+        run: "composer install --no-interaction --no-progress --no-suggest"
+
+      - name: "Install highest dependencies with composer"
+        if: "matrix.dependencies == 'highest'"
+        run: "composer update --no-interaction --no-progress --no-suggest"
 
       - name: "Run maglnet/composer-require-checker"
-        uses: docker://webfactory/composer-require-checker:2.0.0
+        uses: "docker://webfactory/composer-require-checker:2.0.0"
 
   static-code-analysis:
     name: "Static Code Analysis"
 
-    runs-on: ubuntu-latest
+    runs-on: "ubuntu-latest"
 
     strategy:
       matrix:
         php-version:
-          - 7.4
+          - "7.4"
 
         dependencies:
-          - locked
+          - "locked"
 
     steps:
       - name: "Checkout"
-        uses: actions/checkout@v2.0.0
+        uses: "actions/checkout@v2.0.0"
 
       - name: "Install PHP with extensions"
-        uses: shivammathur/setup-php@1.6.1
+        uses: "shivammathur/setup-php@1.7.0"
         with:
-          coverage: none
-          extensions: "mbstring"
-          php-version: ${{ matrix.php-version }}
+          coverage: "none"
+          extensions: "${{ env.REQUIRED_PHP_EXTENSIONS }}"
+          php-version: "${{ matrix.php-version }}"
 
       - name: "Cache dependencies installed with composer"
-        uses: actions/cache@v1.0.3
+        uses: "actions/cache@v1.0.3"
         with:
-          path: ~/.composer/cache
-          key: ${{ matrix.php-version }}-composer-locked-${{ hashFiles('**/composer.lock') }}
-          restore-keys: |
-            ${{ matrix.php-version }}-composer-locked-
+          path: "~/.composer/cache"
+          key: "${{ matrix.php-version }}-composer-locked-${{ hashFiles('**/composer.lock') }}"
+          restore-keys: "${{ matrix.php-version }}-composer-locked-"
+
+      - name: "Install lowest dependencies with composer"
+        if: "matrix.dependencies == 'lowest'"
+        run: "composer update --no-interaction --no-progress --no-suggest --prefer-lowest"
 
       - name: "Install locked dependencies with composer"
-        run: composer install --no-interaction --no-progress --no-suggest
+        if: "matrix.dependencies == 'locked'"
+        run: "composer install --no-interaction --no-progress --no-suggest"
+
+      - name: "Install highest dependencies with composer"
+        if: "matrix.dependencies == 'highest'"
+        run: "composer update --no-interaction --no-progress --no-suggest"
+
+      - name: "Create cache directory for phpstan/phpstan"
+        run: "mkdir -p .build/phpstan"
 
       - name: "Run phpstan/phpstan"
-        run: vendor/bin/phpstan analyse --configuration=phpstan.neon
+        run: "vendor/bin/phpstan analyse --configuration=phpstan.neon"
+
+      - name: "Create cache directory for vimeo/psalm"
+        run: "mkdir -p .build/psalm"
+
+      - name: "Run vimeo/psalm"
+        run: "vendor/bin/psalm --config=psalm.xml"
 
   tests:
     name: "Tests"
 
-    runs-on: ubuntu-latest
+    runs-on: "ubuntu-latest"
 
     strategy:
       matrix:
         php-version:
-          - 7.1
-          - 7.2
-          - 7.3
-          - 7.4
+          - "7.1"
+          - "7.2"
+          - "7.3"
+          - "7.4"
 
         dependencies:
-          - lowest
-          - locked
-          - highest
+          - "lowest"
+          - "locked"
+          - "highest"
 
     steps:
       - name: "Checkout"
-        uses: actions/checkout@v2.0.0
+        uses: "actions/checkout@v2.0.0"
 
       - name: "Install PHP with extensions"
-        uses: shivammathur/setup-php@1.6.1
+        uses: "shivammathur/setup-php@1.7.0"
         with:
-          coverage: none
-          extensions: "mbstring"
-          php-version: ${{ matrix.php-version }}
+          coverage: "none"
+          extensions: "${{ env.REQUIRED_PHP_EXTENSIONS }}"
+          php-version: "${{ matrix.php-version }}"
 
       - name: "Cache dependencies installed with composer"
-        uses: actions/cache@v1.0.3
+        uses: "actions/cache@v1.0.3"
         with:
-          path: ~/.composer/cache
-          key: php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-${{ hashFiles('**/composer.lock') }}
-          restore-keys: |
-            php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-
+          path: "~/.composer/cache"
+          key: "php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-${{ hashFiles('**/composer.lock') }}"
+          restore-keys: "php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-"
 
       - name: "Install lowest dependencies with composer"
-        if: matrix.dependencies == 'lowest'
-        run: composer update --no-interaction --no-progress --no-suggest --prefer-lowest
+        if: "matrix.dependencies == 'lowest'"
+        run: "composer update --no-interaction --no-progress --no-suggest --prefer-lowest"
 
       - name: "Install locked dependencies with composer"
-        if: matrix.dependencies == 'locked'
-        run: composer install --no-interaction --no-progress --no-suggest
+        if: "matrix.dependencies == 'locked'"
+        run: "composer install --no-interaction --no-progress --no-suggest"
 
       - name: "Install highest dependencies with composer"
-        if: matrix.dependencies == 'highest'
-        run: composer update --no-interaction --no-progress --no-suggest
+        if: "matrix.dependencies == 'highest'"
+        run: "composer update --no-interaction --no-progress --no-suggest"
 
       - name: "Run auto-review tests with phpunit/phpunit"
-        run: vendor/bin/phpunit --configuration=test/AutoReview/phpunit.xml
+        run: "vendor/bin/phpunit --configuration=test/AutoReview/phpunit.xml"
 
       - name: "Run unit tests with phpunit/phpunit"
-        run: vendor/bin/phpunit --configuration=test/Unit/phpunit.xml
+        run: "vendor/bin/phpunit --configuration=test/Unit/phpunit.xml"
 
       - name: "Run integration tests with phpunit/phpunit"
-        run: vendor/bin/phpunit --configuration=test/Integration/phpunit.xml
+        run: "vendor/bin/phpunit --configuration=test/Integration/phpunit.xml"
 
   code-coverage:
     name: "Code Coverage"
 
-    runs-on: ubuntu-latest
+    runs-on: "ubuntu-latest"
 
     strategy:
       matrix:
         php-version:
-          - 7.4
+          - "7.4"
 
         dependencies:
-          - locked
+          - "locked"
 
     steps:
       - name: "Checkout"
-        uses: actions/checkout@v2.0.0
+        uses: "actions/checkout@v2.0.0"
 
       - name: "Install PHP with extensions"
-        uses: shivammathur/setup-php@1.6.1
+        uses: "shivammathur/setup-php@1.7.0"
         with:
-          coverage: xdebug
-          extensions: "mbstring"
-          php-version: ${{ matrix.php-version }}
+          coverage: "xdebug"
+          extensions: "${{ env.REQUIRED_PHP_EXTENSIONS }}"
+          php-version: "${{ matrix.php-version }}"
 
       - name: "Cache dependencies installed with composer"
-        uses: actions/cache@v1.0.3
+        uses: "actions/cache@v1.0.3"
         with:
-          path: ~/.composer/cache
-          key: php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-${{ hashFiles('**/composer.lock') }}
-          restore-keys: |
-            php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-
+          path: "~/.composer/cache"
+          key: "php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-${{ hashFiles('**/composer.lock') }}"
+          restore-keys: "php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-"
+
+      - name: "Install lowest dependencies with composer"
+        if: "matrix.dependencies == 'lowest'"
+        run: "composer update --no-interaction --no-progress --no-suggest --prefer-lowest"
 
       - name: "Install locked dependencies with composer"
-        run: composer install --no-interaction --no-progress --no-suggest
+        if: "matrix.dependencies == 'locked'"
+        run: "composer install --no-interaction --no-progress --no-suggest"
+
+      - name: "Install highest dependencies with composer"
+        if: "matrix.dependencies == 'highest'"
+        run: "composer update --no-interaction --no-progress --no-suggest"
 
       - name: "Dump Xdebug filter with phpunit/phpunit"
-        run: vendor/bin/phpunit --configuration=test/Unit/phpunit.xml --dump-xdebug-filter=.build/phpunit/xdebug-filter.php
+        run: "vendor/bin/phpunit --configuration=test/Unit/phpunit.xml --dump-xdebug-filter=.build/phpunit/xdebug-filter.php"
 
       - name: "Collect code coverage with Xdebug and phpunit/phpunit"
-        run: vendor/bin/phpunit --configuration=test/Unit/phpunit.xml --coverage-clover=build/logs/clover.xml --prepend=.build/phpunit/xdebug-filter.php
+        run: "vendor/bin/phpunit --configuration=test/Unit/phpunit.xml --coverage-clover=build/logs/clover.xml --prepend=.build/phpunit/xdebug-filter.php"
 
       - name: "Send code coverage report to Codecov.io"
         env:
-          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
-        run: bash <(curl -s https://codecov.io/bash)
+          CODECOV_TOKEN: "${{ secrets.CODECOV_TOKEN }}"
+        run: "bash <(curl -s https://codecov.io/bash)"
 
   mutation-tests:
     name: "Mutation Tests"
 
-    runs-on: ubuntu-latest
+    runs-on: "ubuntu-latest"
 
     strategy:
       matrix:
         php-version:
-          - 7.4
+          - "7.4"
 
         dependencies:
-          - locked
+          - "locked"
 
     steps:
       - name: "Checkout"
-        uses: actions/checkout@v2.0.0
+        uses: "actions/checkout@v2.0.0"
 
       - name: "Install PHP with extensions"
-        uses: shivammathur/setup-php@1.6.1
+        uses: "shivammathur/setup-php@1.7.0"
         with:
-          coverage: xdebug
-          extensions: "mbstring"
-          php-version: ${{ matrix.php-version }}
+          coverage: "xdebug"
+          extensions: "${{ env.REQUIRED_PHP_EXTENSIONS }}"
+          php-version: "${{ matrix.php-version }}"
 
       - name: "Cache dependencies installed with composer"
-        uses: actions/cache@v1.0.3
+        uses: "actions/cache@v1.0.3"
         with:
-          path: ~/.composer/cache
-          key: php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-${{ hashFiles('**/composer.lock') }}
-          restore-keys: |
-            php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-
+          path: "~/.composer/cache"
+          key: "php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-${{ hashFiles('**/composer.lock') }}"
+          restore-keys: "php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-"
+
+      - name: "Install lowest dependencies with composer"
+        if: "matrix.dependencies == 'lowest'"
+        run: "composer update --no-interaction --no-progress --no-suggest --prefer-lowest"
 
       - name: "Install locked dependencies with composer"
-        run: composer install --no-interaction --no-progress --no-suggest
+        if: "matrix.dependencies == 'locked'"
+        run: "composer install --no-interaction --no-progress --no-suggest"
+
+      - name: "Install highest dependencies with composer"
+        if: "matrix.dependencies == 'highest'"
+        run: "composer update --no-interaction --no-progress --no-suggest"
 
       - name: "Run mutation tests with Xdebug and infection/infection"
-        run: vendor/bin/infection --ignore-msi-with-no-mutations --min-covered-msi=100 --min-msi=100
+        run: "vendor/bin/infection --ignore-msi-with-no-mutations --min-covered-msi=${{ env.MIN_COVERED_MSI }} --min-msi=${{ env.MIN_MSI }}"
diff --git a/.github/workflows/stale.yml b/.github/workflows/stale.yml
index 8125fd9e..582d147a 100644
--- a/.github/workflows/stale.yml
+++ b/.github/workflows/stale.yml
@@ -1,6 +1,6 @@
 # https://github.com/actions/stale
 
-name: "Close stale issues and pull requests"
+name: "Stale"
 
 on:
   schedule:
@@ -8,20 +8,22 @@ on:
 
 jobs:
   stale:
-    runs-on: ubuntu-latest
+    runs-on: "ubuntu-latest"
+
     steps:
-      - uses: actions/stale@v1
+      - name: "Close stale issues and pull requests"
+        uses: "actions/stale@v1.1.0"
         with:
-          repo-token: ${{ secrets.GITHUB_TOKEN }}
-          days-before-stale: 60
           days-before-close: 5
+          days-before-stale: 60
+          repo-token: "${{ secrets.GITHUB_TOKEN }}"
           stale-issue-label: 'stale'
           stale-issue-message: >
             This issue has been automatically marked as stale because it has not had
             recent activity. It will be closed if no further activity occurs. Thank you
             for your contributions.
+          stale-pr-label: "stale"
           stale-pr-message: >
             This PR has been automatically marked as stale because it has not had
             recent activity. It will be closed if no further activity occurs. Thank you
             for your contributions.
-          stale-pr-label: 'stale'
diff --git a/Makefile b/Makefile
index 950cf82a..3e8f8d78 100644
--- a/Makefile
+++ b/Makefile
@@ -1,9 +1,13 @@
+MIN_COVERED_MSI:=100
+MIN_MSI:=100
+
 .PHONY: it
 it: coding-standards dependency-analysis static-code-analysis tests ## Runs the coding-standards, dependency-analysis, static-code-analysis, and tests targets
 
 .PHONY: code-coverage
 code-coverage: vendor ## Collects coverage from running unit tests with phpunit/phpunit
-	vendor/bin/phpunit --configuration=test/Unit/phpunit.xml --coverage-text
+	vendor/bin/phpunit --configuration=test/Unit/phpunit.xml --dump-xdebug-filter=.build/phpunit/xdebug-filter.php
+	vendor/bin/phpunit --configuration=test/Unit/phpunit.xml --coverage-text --prepend=.build/phpunit/xdebug-filter.php
 
 .PHONY: coding-standards
 coding-standards: vendor ## Fixes code style issues with friendsofphp/php-cs-fixer
@@ -21,18 +25,22 @@ help: ## Displays this list of targets with descriptions
 .PHONY: mutation-tests
 mutation-tests: vendor ## Runs mutation tests with infection/infection
 	mkdir -p .build/infection
-	vendor/bin/infection --ignore-msi-with-no-mutations --min-covered-msi=100 --min-msi=100
+	vendor/bin/infection --ignore-msi-with-no-mutations --min-covered-msi=${MIN_COVERED_MSI} --min-msi=${MIN_MSI}
 
 .PHONY: static-code-analysis
-static-code-analysis: vendor ## Runs a static code analysis with phpstan/phpstan
+static-code-analysis: vendor ## Runs a static code analysis with phpstan/phpstan and vimeo/psalm
 	mkdir -p .build/phpstan
 	vendor/bin/phpstan analyse --configuration=phpstan.neon
+	mkdir -p .build/psalm
+	vendor/bin/psalm --config=psalm.xml
 
 .PHONY: static-code-analysis-baseline
-static-code-analysis-baseline: vendor ## Generates a baseline for static code analysis with phpstan/phpstan
+static-code-analysis-baseline: vendor ## Generates a baseline for static code analysis with phpstan/phpstan and vimeo/psalm
 	mkdir -p .build/phpstan
 	echo '' > phpstan-baseline.neon
 	vendor/bin/phpstan analyze --configuration=phpstan.neon --error-format=baselineNeon > phpstan-baseline.neon || true
+	mkdir -p .build/psalm
+	vendor/bin/psalm --config=psalm.xml --set-baseline=psalm-baseline.xml
 
 .PHONY: tests
 tests: vendor ## Runs auto-review, unit, and integration tests with phpunit/phpunit
diff --git a/composer.json b/composer.json
index c85d1432..45f5b9b7 100644
--- a/composer.json
+++ b/composer.json
@@ -25,7 +25,9 @@
     "phpstan/phpstan-deprecation-rules": "~0.12.0",
     "phpstan/phpstan-phpunit": "~0.12.3",
     "phpstan/phpstan-strict-rules": "~0.12.0",
-    "phpunit/phpunit": "^7.5.18"
+    "phpunit/phpunit": "^7.5.18",
+    "psalm/plugin-phpunit": "~0.8.0",
+    "vimeo/psalm": "^3.8.1"
   },
   "config": {
     "preferred-install": "dist",
diff --git a/composer.lock b/composer.lock
index b26d9598..10d4486f 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "2980fc89861a449c1d88ec44e0a32790",
+    "content-hash": "0e22476b9fe63a75a739d6cbd9b6bc46",
     "packages": [
         {
             "name": "composer/semver",
@@ -1326,6 +1326,142 @@
         }
     ],
     "packages-dev": [
+        {
+            "name": "amphp/amp",
+            "version": "v2.4.0",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/amphp/amp.git",
+                "reference": "13930a582947831bb66ff1aeac28672fd91c38ea"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/amphp/amp/zipball/13930a582947831bb66ff1aeac28672fd91c38ea",
+                "reference": "13930a582947831bb66ff1aeac28672fd91c38ea",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=7"
+            },
+            "require-dev": {
+                "amphp/php-cs-fixer-config": "dev-master",
+                "amphp/phpunit-util": "^1",
+                "ext-json": "*",
+                "phpstan/phpstan": "^0.8.5",
+                "phpunit/phpunit": "^6.0.9 | ^7",
+                "react/promise": "^2"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "2.0.x-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Amp\\": "lib"
+                },
+                "files": [
+                    "lib/functions.php",
+                    "lib/Internal/functions.php"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Daniel Lowrey",
+                    "email": "rdlowrey@php.net"
+                },
+                {
+                    "name": "Aaron Piotrowski",
+                    "email": "aaron@trowski.com"
+                },
+                {
+                    "name": "Bob Weinand",
+                    "email": "bobwei9@hotmail.com"
+                },
+                {
+                    "name": "Niklas Keller",
+                    "email": "me@kelunik.com"
+                }
+            ],
+            "description": "A non-blocking concurrency framework for PHP applications.",
+            "homepage": "http://amphp.org/amp",
+            "keywords": [
+                "async",
+                "asynchronous",
+                "awaitable",
+                "concurrency",
+                "event",
+                "event-loop",
+                "future",
+                "non-blocking",
+                "promise"
+            ],
+            "time": "2019-11-11T19:32:05+00:00"
+        },
+        {
+            "name": "amphp/byte-stream",
+            "version": "v1.7.1",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/amphp/byte-stream.git",
+                "reference": "9d8205686a004948475dc43f8a88d2fa5e75a113"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/amphp/byte-stream/zipball/9d8205686a004948475dc43f8a88d2fa5e75a113",
+                "reference": "9d8205686a004948475dc43f8a88d2fa5e75a113",
+                "shasum": ""
+            },
+            "require": {
+                "amphp/amp": "^2"
+            },
+            "require-dev": {
+                "amphp/php-cs-fixer-config": "dev-master",
+                "amphp/phpunit-util": "^1",
+                "friendsofphp/php-cs-fixer": "^2.3",
+                "infection/infection": "^0.9.3",
+                "phpunit/phpunit": "^6"
+            },
+            "type": "library",
+            "autoload": {
+                "psr-4": {
+                    "Amp\\ByteStream\\": "lib"
+                },
+                "files": [
+                    "lib/functions.php"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Aaron Piotrowski",
+                    "email": "aaron@trowski.com"
+                },
+                {
+                    "name": "Niklas Keller",
+                    "email": "me@kelunik.com"
+                }
+            ],
+            "description": "A stream abstraction to make working with non-blocking I/O simple.",
+            "homepage": "http://amphp.org/byte-stream",
+            "keywords": [
+                "amp",
+                "amphp",
+                "async",
+                "io",
+                "non-blocking",
+                "stream"
+            ],
+            "time": "2019-10-27T14:33:41+00:00"
+        },
         {
             "name": "composer/ca-bundle",
             "version": "1.2.5",
@@ -1844,6 +1980,94 @@
             ],
             "time": "2019-12-19T09:08:28+00:00"
         },
+        {
+            "name": "felixfbecker/advanced-json-rpc",
+            "version": "v3.0.4",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/felixfbecker/php-advanced-json-rpc.git",
+                "reference": "23366dd0cab0a0f3fd3016bf3c0b36dec74348e7"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/felixfbecker/php-advanced-json-rpc/zipball/23366dd0cab0a0f3fd3016bf3c0b36dec74348e7",
+                "reference": "23366dd0cab0a0f3fd3016bf3c0b36dec74348e7",
+                "shasum": ""
+            },
+            "require": {
+                "netresearch/jsonmapper": "^1.0",
+                "php": ">=7.0",
+                "phpdocumentor/reflection-docblock": "^4.0.0"
+            },
+            "require-dev": {
+                "phpunit/phpunit": "^6.0.0"
+            },
+            "type": "library",
+            "autoload": {
+                "psr-4": {
+                    "AdvancedJsonRpc\\": "lib/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "ISC"
+            ],
+            "authors": [
+                {
+                    "name": "Felix Becker",
+                    "email": "felix.b@outlook.com"
+                }
+            ],
+            "description": "A more advanced JSONRPC implementation",
+            "time": "2019-09-12T22:41:08+00:00"
+        },
+        {
+            "name": "felixfbecker/language-server-protocol",
+            "version": "v1.4.0",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/felixfbecker/php-language-server-protocol.git",
+                "reference": "378801f6139bb74ac215d81cca1272af61df9a9f"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/felixfbecker/php-language-server-protocol/zipball/378801f6139bb74ac215d81cca1272af61df9a9f",
+                "reference": "378801f6139bb74ac215d81cca1272af61df9a9f",
+                "shasum": ""
+            },
+            "require": {
+                "php": "^7.0"
+            },
+            "require-dev": {
+                "phpstan/phpstan": "*",
+                "phpunit/phpunit": "^6.3",
+                "squizlabs/php_codesniffer": "^3.1"
+            },
+            "type": "library",
+            "autoload": {
+                "psr-4": {
+                    "LanguageServerProtocol\\": "src/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "ISC"
+            ],
+            "authors": [
+                {
+                    "name": "Felix Becker",
+                    "email": "felix.b@outlook.com"
+                }
+            ],
+            "description": "PHP classes for the Language Server Protocol",
+            "keywords": [
+                "language",
+                "microsoft",
+                "php",
+                "server"
+            ],
+            "time": "2019-06-23T21:03:50+00:00"
+        },
         {
             "name": "fzaninotto/faker",
             "version": "v1.9.1",
@@ -2365,6 +2589,52 @@
             ],
             "time": "2019-12-15T19:12:40+00:00"
         },
+        {
+            "name": "netresearch/jsonmapper",
+            "version": "v1.6.0",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/cweiske/jsonmapper.git",
+                "reference": "0d4d1b48d682a93b6bfedf60b88c7750e9cb0b06"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/cweiske/jsonmapper/zipball/0d4d1b48d682a93b6bfedf60b88c7750e9cb0b06",
+                "reference": "0d4d1b48d682a93b6bfedf60b88c7750e9cb0b06",
+                "shasum": ""
+            },
+            "require": {
+                "ext-json": "*",
+                "ext-pcre": "*",
+                "ext-reflection": "*",
+                "ext-spl": "*",
+                "php": ">=5.6"
+            },
+            "require-dev": {
+                "phpunit/phpunit": "~4.8.35 || ~5.7 || ~6.4",
+                "squizlabs/php_codesniffer": "~1.5"
+            },
+            "type": "library",
+            "autoload": {
+                "psr-0": {
+                    "JsonMapper": "src/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "OSL-3.0"
+            ],
+            "authors": [
+                {
+                    "name": "Christian Weiske",
+                    "email": "cweiske@cweiske.de",
+                    "homepage": "http://github.com/cweiske/jsonmapper/",
+                    "role": "Developer"
+                }
+            ],
+            "description": "Map nested JSON structures onto PHP classes",
+            "time": "2019-08-15T19:41:25+00:00"
+        },
         {
             "name": "nikic/php-parser",
             "version": "v4.3.0",
@@ -2467,6 +2737,55 @@
             "description": "Composer plugin that provides efficient querying for installed package versions (no runtime IO)",
             "time": "2019-11-15T16:17:10+00:00"
         },
+        {
+            "name": "openlss/lib-array2xml",
+            "version": "1.0.0",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/nullivex/lib-array2xml.git",
+                "reference": "a91f18a8dfc69ffabe5f9b068bc39bb202c81d90"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/nullivex/lib-array2xml/zipball/a91f18a8dfc69ffabe5f9b068bc39bb202c81d90",
+                "reference": "a91f18a8dfc69ffabe5f9b068bc39bb202c81d90",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=5.3.2"
+            },
+            "type": "library",
+            "autoload": {
+                "psr-0": {
+                    "LSS": ""
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "Apache-2.0"
+            ],
+            "authors": [
+                {
+                    "name": "Bryan Tong",
+                    "email": "bryan@nullivex.com",
+                    "homepage": "https://www.nullivex.com"
+                },
+                {
+                    "name": "Tony Butler",
+                    "email": "spudz76@gmail.com",
+                    "homepage": "https://www.nullivex.com"
+                }
+            ],
+            "description": "Array2XML conversion library credit to lalit.org",
+            "homepage": "https://www.nullivex.com",
+            "keywords": [
+                "array",
+                "array conversion",
+                "xml",
+                "xml conversion"
+            ],
+            "time": "2019-03-29T20:06:56+00:00"
+        },
         {
             "name": "padraic/humbug_get_contents",
             "version": "1.1.2",
@@ -3534,6 +3853,63 @@
             ],
             "time": "2018-01-21T07:42:36+00:00"
         },
+        {
+            "name": "psalm/plugin-phpunit",
+            "version": "0.8.0",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/psalm/phpunit-psalm-plugin.git",
+                "reference": "1dcd8ff7719b78b858d7560dd2d912a55272bfbc"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/psalm/phpunit-psalm-plugin/zipball/1dcd8ff7719b78b858d7560dd2d912a55272bfbc",
+                "reference": "1dcd8ff7719b78b858d7560dd2d912a55272bfbc",
+                "shasum": ""
+            },
+            "require": {
+                "composer/semver": "^1.4",
+                "ocramius/package-versions": "^1.3",
+                "phpunit/phpunit": "^6.0 || ^7.0 || ^8.0",
+                "vimeo/psalm": "^3.6.2 || dev-master"
+            },
+            "require-dev": {
+                "codeception/base": "^2.5",
+                "squizlabs/php_codesniffer": "^3.3.1",
+                "weirdan/codeception-psalm-module": "^0.2.2"
+            },
+            "type": "psalm-plugin",
+            "extra": {
+                "psalm": {
+                    "pluginClass": "Psalm\\PhpUnitPlugin\\Plugin"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Psalm\\PhpUnitPlugin\\": [
+                        "."
+                    ],
+                    "Psalm\\PhpUnitPlugin\\Hooks\\": [
+                        "hooks"
+                    ],
+                    "Psalm\\PhpUnitPlugin\\Exception\\": [
+                        "Exception"
+                    ]
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Matt Brown",
+                    "email": "github@muglug.com"
+                }
+            ],
+            "description": "Psalm plugin for PHPUnit",
+            "time": "2019-11-27T15:49:38+00:00"
+        },
         {
             "name": "sebastian/code-unit-reverse-lookup",
             "version": "1.0.1",
@@ -4199,6 +4575,97 @@
             "description": "A small library for converting tokenized PHP source code into XML and potentially other formats",
             "time": "2019-06-13T22:48:21+00:00"
         },
+        {
+            "name": "vimeo/psalm",
+            "version": "3.8.1",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/vimeo/psalm.git",
+                "reference": "8e54e3aa060fc490d86d0e2abbf62750516d40fd"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/vimeo/psalm/zipball/8e54e3aa060fc490d86d0e2abbf62750516d40fd",
+                "reference": "8e54e3aa060fc490d86d0e2abbf62750516d40fd",
+                "shasum": ""
+            },
+            "require": {
+                "amphp/amp": "^2.1",
+                "amphp/byte-stream": "^1.5",
+                "composer/xdebug-handler": "^1.1",
+                "ext-dom": "*",
+                "felixfbecker/advanced-json-rpc": "^3.0.3",
+                "felixfbecker/language-server-protocol": "^1.4",
+                "netresearch/jsonmapper": "^1.0",
+                "nikic/php-parser": "^4.3",
+                "ocramius/package-versions": "^1.2",
+                "openlss/lib-array2xml": "^1.0",
+                "php": "^7.1.3",
+                "sebastian/diff": "^3.0",
+                "symfony/console": "^3.3||^4.0||^5.0",
+                "webmozart/glob": "^4.1",
+                "webmozart/path-util": "^2.3"
+            },
+            "provide": {
+                "psalm/psalm": "self.version"
+            },
+            "require-dev": {
+                "bamarni/composer-bin-plugin": "^1.2",
+                "ext-curl": "*",
+                "friendsofphp/php-cs-fixer": "^2.15",
+                "phpmyadmin/sql-parser": "^5.0",
+                "phpspec/prophecy": ">=1.9.0",
+                "phpunit/phpunit": "^7.5 || ^8.0",
+                "psalm/plugin-phpunit": "^0.6",
+                "slevomat/coding-standard": "^5.0",
+                "squizlabs/php_codesniffer": "^3.5",
+                "symfony/process": "^4.3"
+            },
+            "suggest": {
+                "ext-igbinary": "^2.0.5"
+            },
+            "bin": [
+                "psalm",
+                "psalter",
+                "psalm-language-server",
+                "psalm-plugin",
+                "psalm-refactor"
+            ],
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "3.x-dev",
+                    "dev-2.x": "2.x-dev",
+                    "dev-1.x": "1.x-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Psalm\\Plugin\\": "src/Psalm/Plugin",
+                    "Psalm\\": "src/Psalm"
+                },
+                "files": [
+                    "src/functions.php",
+                    "src/spl_object_id.php"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Matthew Brown"
+                }
+            ],
+            "description": "A static analysis tool for finding errors in PHP applications",
+            "keywords": [
+                "code",
+                "inspection",
+                "php"
+            ],
+            "time": "2019-12-29T16:11:07+00:00"
+        },
         {
             "name": "webmozart/assert",
             "version": "1.6.0",
@@ -4246,6 +4713,99 @@
                 "validate"
             ],
             "time": "2019-11-24T13:36:37+00:00"
+        },
+        {
+            "name": "webmozart/glob",
+            "version": "4.1.0",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/webmozart/glob.git",
+                "reference": "3cbf63d4973cf9d780b93d2da8eec7e4a9e63bbe"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/webmozart/glob/zipball/3cbf63d4973cf9d780b93d2da8eec7e4a9e63bbe",
+                "reference": "3cbf63d4973cf9d780b93d2da8eec7e4a9e63bbe",
+                "shasum": ""
+            },
+            "require": {
+                "php": "^5.3.3|^7.0",
+                "webmozart/path-util": "^2.2"
+            },
+            "require-dev": {
+                "phpunit/phpunit": "^4.6",
+                "sebastian/version": "^1.0.1",
+                "symfony/filesystem": "^2.5"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "4.1-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Webmozart\\Glob\\": "src/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Bernhard Schussek",
+                    "email": "bschussek@gmail.com"
+                }
+            ],
+            "description": "A PHP implementation of Ant's glob.",
+            "time": "2015-12-29T11:14:33+00:00"
+        },
+        {
+            "name": "webmozart/path-util",
+            "version": "2.3.0",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/webmozart/path-util.git",
+                "reference": "d939f7edc24c9a1bb9c0dee5cb05d8e859490725"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/webmozart/path-util/zipball/d939f7edc24c9a1bb9c0dee5cb05d8e859490725",
+                "reference": "d939f7edc24c9a1bb9c0dee5cb05d8e859490725",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=5.3.3",
+                "webmozart/assert": "~1.0"
+            },
+            "require-dev": {
+                "phpunit/phpunit": "^4.6",
+                "sebastian/version": "^1.0.1"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "2.3-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Webmozart\\PathUtil\\": "src/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Bernhard Schussek",
+                    "email": "bschussek@gmail.com"
+                }
+            ],
+            "description": "A robust cross-platform utility for normalizing, comparing and modifying file paths.",
+            "time": "2015-12-17T08:42:14+00:00"
         }
     ],
     "aliases": [],
diff --git a/phpstan-baseline.neon b/phpstan-baseline.neon
index 14f99ef3..42b9e0a2 100644
--- a/phpstan-baseline.neon
+++ b/phpstan-baseline.neon
@@ -20,8 +20,3 @@ parameters:
 			count: 1
 			path: test/Unit/RuleSet/AbstractRuleSetTestCase.php
 
-		-
-			message: "#^Parameter \\#1 \\$argument of class ReflectionClass constructor expects class\\-string\\<T of object\\>\\|T of object, string given\\.$#"
-			count: 1
-			path: test/Unit/RuleSet/AbstractRuleSetTestCase.php
-
diff --git a/psalm-baseline.xml b/psalm-baseline.xml
new file mode 100644
index 00000000..b0a8d767
--- /dev/null
+++ b/psalm-baseline.xml
@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<files psalm-version="3.8.1@8e54e3aa060fc490d86d0e2abbf62750516d40fd">
+  <file src="test/Unit/RuleSet/AbstractRuleSetTestCase.php">
+    <InternalClass occurrences="2">
+      <code>FixerFactory::create()</code>
+      <code>RuleSet::create($rules)</code>
+    </InternalClass>
+    <InternalMethod occurrences="4">
+      <code>FixerFactory::create()</code>
+      <code>registerBuiltInFixers</code>
+      <code>getFixers</code>
+      <code>RuleSet::create($rules)</code>
+    </InternalMethod>
+  </file>
+</files>
diff --git a/psalm.xml b/psalm.xml
new file mode 100644
index 00000000..87dbffbd
--- /dev/null
+++ b/psalm.xml
@@ -0,0 +1,24 @@
+<?xml version="1.0"?>
+<psalm
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xmlns="https://getpsalm.org/schema/config"
+    xsi:schemaLocation="https://getpsalm.org/schema/config vendor/vimeo/psalm/config.xsd"
+    errorBaseline="psalm-baseline.xml"
+    resolveFromConfigFile="true"
+>
+    <issueHandlers>
+        <LessSpecificReturnType errorLevel="info" />
+    </issueHandlers>
+
+    <plugins>
+        <pluginClass class="Psalm\PhpUnitPlugin\Plugin" />
+    </plugins>
+
+    <projectFiles>
+        <directory name="src" />
+        <directory name="test" />
+        <ignoreFiles>
+            <directory name="vendor" />
+        </ignoreFiles>
+    </projectFiles>
+</psalm>
diff --git a/src/RuleSet/AbstractRuleSet.php b/src/RuleSet/AbstractRuleSet.php
index 154d4f37..e7ac3134 100644
--- a/src/RuleSet/AbstractRuleSet.php
+++ b/src/RuleSet/AbstractRuleSet.php
@@ -23,7 +23,7 @@ abstract class AbstractRuleSet implements RuleSet
     /**
      * @var string
      */
-    protected $name;
+    protected $name = '';
 
     /**
      * @var array
@@ -33,7 +33,7 @@ abstract class AbstractRuleSet implements RuleSet
     /**
      * @var int
      */
-    protected $targetPhpVersion;
+    protected $targetPhpVersion = 0;
 
     final public function __construct(?string $header = null)
     {
diff --git a/test/Unit/RuleSet/AbstractRuleSetTestCase.php b/test/Unit/RuleSet/AbstractRuleSetTestCase.php
index 4f6c29e5..871b0bf9 100644
--- a/test/Unit/RuleSet/AbstractRuleSetTestCase.php
+++ b/test/Unit/RuleSet/AbstractRuleSetTestCase.php
@@ -127,10 +127,10 @@ final public function providerValidHeader(): \Generator
     /**
      * @dataProvider providerRuleNames
      *
-     * @param array  $ruleNames
-     * @param string $source
+     * @param string   $source
+     * @param string[] $ruleNames
      */
-    final public function testRulesAreSortedByName($source, $ruleNames): void
+    final public function testRulesAreSortedByName(string $source, array $ruleNames): void
     {
         $sorted = $ruleNames;
 
@@ -193,6 +193,7 @@ final protected static function className(): string
      */
     final protected static function createRuleSet($header = null): Config\RuleSet
     {
+        /** @var class-string $className */
         $className = self::className();
 
         $reflection = new \ReflectionClass($className);
@@ -236,7 +237,7 @@ private function configuredFixers(): array
          *
          * @see https://github.com/FriendsOfPHP/PHP-CS-Fixer/pull/2361
          */
-        $rules = \array_map(static function (): bool {
+        $rules = \array_map(static function ($ruleConfiguration): bool {
             return true;
         }, self::createRuleSet()->rules());