test: separate cases, so it's easier to know what fails

.markdownlint-cli2.jsonc

@@ -6,6 +6,6 @@
     "MD033": false
   },
   "globs": ["**/*.{md,mdx}"],
-  "ignores": ["**/node_modules", "**/test/fixtures"],
+  "ignores": ["**/node_modules", "**/test/fixtures/**"],
   "customRules": ["./src/index.js"]
 }

package.json

@@ -37,7 +37,7 @@
     "lint:prettier": "prettier . --check --ignore-path .gitignore",
     "lint:javascript": "tsc --project jsconfig.json --noEmit",
     "lint:staged": "lint-staged",
-    "test": "node --test ./test",
+    "test": "node --test --experimental-test-coverage ./test",
     "release": "semantic-release",
     "postinstall": "husky install",
     "prepublishOnly": "pinst --disable",

test/fixtures/invalid/non-existing-file.md

@@ -0,0 +1,3 @@
+# Invalid
+
+[File](./index.test.js)

test/fixtures/invalid/non-existing-heading-fragment/awesome.md

@@ -0,0 +1,3 @@
+# Valid
+
+## Existing Heading

test/fixtures/invalid/non-existing-heading-fragment/non-existing-heading-fragment.md

@@ -0,0 +1,3 @@
+# Invalid
+
+[Link fragment](./awesome.md#non-existing-heading)

test/fixtures/invalid/non-existing-image.md

@@ -0,0 +1,3 @@
+# Invalid
+
+![Image](./image.png)

test/fixtures/valid/existing-file.md

@@ -0,0 +1,3 @@
+# Valid
+
+[File](../../index.test.js)

test/fixtures/valid/existing-heading-fragment/awesome.md

@@ -0,0 +1,13 @@
+# Valid
+
+## Existing Heading
+
+### Repeated Heading
+
+Text
+
+### Repeated Heading
+
+Text
+
+### Repeated Heading

test/fixtures/valid/existing-heading-fragment/existing-heading-fragment.md

@@ -0,0 +1,9 @@
+# Valid
+
+[Link fragment](./awesome.md#existing-heading)
+
+[Link fragment Repeated 0](./awesome.md#repeated-heading)
+
+[Link fragment Repeated 1](./awesome.md#repeated-heading-1)
+
+[Link fragment Repeated 2](./awesome.md#repeated-heading-2)

test/fixtures/valid/existing-image.md

@@ -0,0 +1,3 @@
+# Valid
+
+![Image](./image.png)

test/fixtures/valid/ignore-absolute-paths.md

@@ -0,0 +1,3 @@
+# Valid
+
+![Absolute Path](/absolute/path.png)

test/fixtures/valid/ignore-external-links.md

@@ -0,0 +1,7 @@
+# Valid
+
+[External https link](https://example.com/)
+
+[External https link 2](https:./external.https)
+
+[External ftp link](ftp:./external.ftp)

test/index.test.js

@@ -0,0 +1,112 @@
+const { test } = require("node:test")
+const assert = require("node:assert/strict")
+
+const { markdownlint } = require("markdownlint").promises
+
+const relativeLinksRule = require("../src/index.js")
+
+/**
+ *
+ * @param {string} fixtureFile
+ * @returns
+ */
+const validateMarkdownLint = async (fixtureFile) => {
+  const lintResults = await markdownlint({
+    files: [fixtureFile],
+    config: {
+      default: false,
+      "relative-links": true,
+    },
+    customRules: [relativeLinksRule],
+  })
+  return lintResults[fixtureFile]
+}
+
+test("ensure the rule validates correctly", async (t) => {
+  await t.test("should be valid", async (t) => {
+    await t.test("with an existing heading fragment", async () => {
+      const lintResults = await validateMarkdownLint(
+        "test/fixtures/valid/existing-heading-fragment/existing-heading-fragment.md",
+      )
+      assert.equal(lintResults?.length, 0)
+    })
+
+    await t.test("with an existing file", async () => {
+      const lintResults = await validateMarkdownLint(
+        "test/fixtures/valid/existing-file.md",
+      )
+      assert.equal(lintResults?.length, 0)
+    })
+
+    await t.test("with an existing image", async () => {
+      const lintResults = await validateMarkdownLint(
+        "test/fixtures/valid/existing-image.md",
+      )
+      assert.equal(lintResults?.length, 0)
+    })
+
+    await t.test("should ignore absolute paths", async () => {
+      const lintResults = await validateMarkdownLint(
+        "test/fixtures/valid/ignore-absolute-paths.md",
+      )
+      assert.equal(lintResults?.length, 0)
+    })
+
+    await t.test("should ignore external links", async () => {
+      const lintResults = await validateMarkdownLint(
+        "test/fixtures/valid/ignore-external-links.md",
+      )
+      assert.equal(lintResults?.length, 0)
+    })
+  })
+
+  await t.test("should be invalid", async (t) => {
+    await t.test("with a non-existing heading fragment", async () => {
+      const lintResults = await validateMarkdownLint(
+        "test/fixtures/invalid/non-existing-heading-fragment/non-existing-heading-fragment.md",
+      )
+      assert.equal(lintResults?.length, 1)
+      assert.deepEqual(lintResults?.[0]?.ruleNames, relativeLinksRule.names)
+      assert.equal(
+        lintResults?.[0]?.ruleDescription,
+        relativeLinksRule.description,
+      )
+      assert.equal(
+        lintResults?.[0]?.errorDetail,
+        '"./awesome.md#non-existing-heading" should have a valid fragment identifier',
+      )
+    })
+
+    await t.test("with a non-existing file", async () => {
+      const lintResults = await validateMarkdownLint(
+        "test/fixtures/invalid/non-existing-file.md",
+      )
+      assert.equal(lintResults?.length, 1)
+      assert.deepEqual(lintResults?.[0]?.ruleNames, relativeLinksRule.names)
+      assert.equal(
+        lintResults?.[0]?.ruleDescription,
+        relativeLinksRule.description,
+      )
+      assert.equal(
+        lintResults?.[0]?.errorDetail,
+        '"./index.test.js" should exist in the file system',
+      )
+    })
+
+    await t.test("with a non-existing image", async () => {
+      const lintResults = await validateMarkdownLint(
+        "test/fixtures/invalid/non-existing-image.md",
+      )
+      assert.equal(lintResults?.length, 1)
+      assert.deepEqual(lintResults?.[0]?.ruleNames, relativeLinksRule.names)
+      assert.equal(
+        lintResults?.[0]?.ruleDescription,
+        relativeLinksRule.description,
+      )
+      assert.equal(
+        lintResults?.[0]?.errorDetail,
+        '"./image.png" should exist in the file system',
+      )
+    })
+  })
+})