Unit test to keep README up-to-date, closes #13

Run this to rewrite the README in place to fix it:

    pytest --rewrite-readme

README.md

@@ -42,29 +42,20 @@ The `--project` argument is required - it specifies the project name that should
 
 ```
 $ datasette publish now2 --help
+
 Usage: datasette publish now2 [OPTIONS] [FILES]...
 
 Options:
-  -m, --metadata FILENAME         Path to JSON/YAML file containing metadata
-                                  to publish
-
+  -m, --metadata FILENAME         Path to JSON/YAML file containing metadata to publish
   --extra-options TEXT            Extra options to pass to datasette serve
-  --branch TEXT                   Install datasette from a GitHub branch e.g.
-                                  master
-
-  --template-dir DIRECTORY        Path to directory containing custom
-                                  templates
-
+  --branch TEXT                   Install datasette from a GitHub branch e.g. master
+  --template-dir DIRECTORY        Path to directory containing custom templates
   --plugins-dir DIRECTORY         Path to directory containing custom plugins
-  --static MOUNT:DIRECTORY        Serve static files from this directory at
-                                  /MOUNT/...
-
-  --install TEXT                  Additional packages (e.g. plugins) to
-                                  install
-
+  --static MOUNT:DIRECTORY        Serve static files from this directory at /MOUNT/...
+  --install TEXT                  Additional packages (e.g. plugins) to install
   --plugin-secret <TEXT TEXT TEXT>...
-                                  Secrets to pass to plugins, e.g. --plugin-
-                                  secret datasette-auth-github client_id xxx
+                                  Secrets to pass to plugins, e.g. --plugin-secret
+                                  datasette-auth-github client_id xxx
 
   --version-note TEXT             Additional note to show on /-/versions
   --title TEXT                    Title for metadata

tests/conftest.py

@@ -0,0 +1,7 @@
+def pytest_addoption(parser):
+    parser.addoption(
+        "--rewrite-readme",
+        action="store_true",
+        default=False,
+        help="Rewrite README on error",
+    )

tests/test_publish_now.py

@@ -1,6 +1,8 @@
 from click.testing import CliRunner
 from datasette import cli
 from unittest import mock
+import pathlib
+import re
 import subprocess
 
 
@@ -60,3 +62,30 @@ def test_publish_now_public(mock_run, mock_which):
         mock_run.assert_has_calls(
             [mock.call(["now", "--confirm", "--no-clipboard", "--prod", "--public"]),]
         )
+
+
+def test_help_in_readme(request):
+    # Ensure the --help output embedded in the README is up-to-date
+    readme_path = pathlib.Path(__file__).parent.parent / "README.md"
+    readme = readme_path.read_text()
+    block_re = re.compile("```(.*)```", re.DOTALL)
+    expected = block_re.search(readme).group(1).strip()
+    runner = CliRunner()
+    result = runner.invoke(cli.cli, ["publish", "now2", "--help"], terminal_width=88)
+    actual = "$ datasette publish now2 --help\n\n{}".format(result.output)
+
+    if request.config.getoption("--rewrite-readme"):
+        readme_path.write_text(
+            block_re.sub(
+                "```\n{}```".format(actual).replace("Usage: cli", "Usage: datasette"),
+                readme,
+            )
+        )
+        return
+
+    # actual has "Usage: cli package [OPTIONS] FILES"
+    # because it doesn't know that cli will be aliased to datasette
+    expected = expected.replace("Usage: datasette", "Usage: cli")
+    assert (
+        expected.strip() == actual.strip()
+    ), "README out of date - try runnning: pytest --rewrite-readme"