Clean up the test harness a bit (#55)

Primarily, this gets rid of the `test/runtest` executable, preventing
the need for spawning an additional subprocess for each test. The
current approach handles all the things that `test/runtest` would in a
`--require` and in a loader that switches whether or not to use the IITM
loader via the same filename check that was originally done in
`test/runtest`.

One interesting thing that happened while making this change is that we
need some way of passing the entrypoint filename to the loader. Since
newer versions of Node.js run the loader in a separate thread,
`process.argv[1]` no longer works. The approved alternative is to use
inter-thread messages via the `register()` method, but that's not
available on some versions of Node.js that also use loader threads. To
get around this, an environment variable is set in the `--require`
that's then propagated to the loader thread. This is a bit hacky, but
probably the only thing that will work across the supported version
range.

An attempt was made to use the more popular `tap` test package, rather
than `imhotap`, but there's no version of `tap` that supports both the
entire Node.js version range that IITM supports _and_ also supports ESM.
For now, this means sticking with `imhotap`, but were it not for the
incompatibility, `tap` would be just as suitable here, and is a much
more popular test package.

Author: bengl

package.json

@@ -4,9 +4,9 @@
   "description": "Intercept imports in Node.js",
   "main": "index.js",
   "scripts": {
-    "test": "c8 --reporter lcov --check-coverage --lines 50 imhotap --runner 'node test/runtest' --files test/{hook,low-level,other,get-esm-exports}/*",
-    "test:ts": "c8 --reporter lcov imhotap --runner 'node test/runtest' --files test/typescript/*.test.mts",
-    "coverage": "c8 --reporter html imhotap --runner 'node test/runtest' --files test/{hook,low-level,other,get-esm-exports}/* && echo '\nNow open coverage/index.html\n'",
+    "test": "c8 --reporter lcov --check-coverage --lines 50 imhotap --files test/{hook,low-level,other,get-esm-exports}/*",
+    "test:ts": "c8 --reporter lcov imhotap --files test/typescript/*.test.mts",
+    "coverage": "c8 --reporter html imhotap --files test/{hook,low-level,other,get-esm-exports}/* && echo '\nNow open coverage/index.html\n'",
     "lint": "eslint .",
     "lint:fix": "eslint . --fix"
   },
@@ -28,6 +28,10 @@
     "url": "https://github.com/DataDog/import-in-the-middle/issues"
   },
   "homepage": "https://github.com/DataDog/import-in-the-middle#readme",
+  "imhotap": {
+    "runner": "node",
+    "test-env": "NODE_OPTIONS=--no-warnings --require ./test/version-check.js --experimental-loader ./test/generic-loader.mjs"
+  },
   "devDependencies": {
     "@babel/core": "^7.23.7",
     "@babel/eslint-parser": "^7.23.3",

test/README.md

@@ -3,11 +3,15 @@ These tests are organized as follows:
 * Located in the `hook` directory if they use the `Hook` class.
 * Located in the `low-level` directory if they use the "low-level" API,
   `addHook` and `removeHook`.
+* Other tests are in other adjacent directories.
 
-The tests should be run with the `runtest` command found in this directory. If
-the command exits with a non-zero code, then it's a test failure.
+The tests can be run individually as Node.js programs with non-zero exit codes
+upon failures. They should be run with the following Node.js command-line
+options (assuming they're run from the project root):
 
-Running of all the tests can be done with `npm test`.
+```
+--require ./test/version-check.js
+--experimental-loader ./test/generic-loader.mmjs
+```
 
-Coverage must be 100% according to `c8`. If you don't have 100% coverage, you
-can run `npm run coverage` to get coverage data in HTML form.
+The entire test suite can be run with `npm test`.

test/generic-loader.mjs

@@ -0,0 +1,14 @@
+// Unless explicitly stated otherwise all files in this repository are licensed under the Apache 2.0 License.
+//
+// This product includes software developed at Datadog (https://www.datadoghq.com/). Copyright 2024 Datadog, Inc.
+
+import * as tsLoader from './typescript/iitm-ts-node-loader.mjs'
+import * as regularLoader from '../hook.mjs'
+import path from 'path'
+
+const filename = process.env.IITM_TEST_FILE
+
+export const { load, resolve, getFormat, getSource } =
+  filename.includes('disabled')
+    ? {}
+    : (path.extname(filename).slice(-2) === 'ts' ? tsLoader : regularLoader)

test/runtest

@@ -0,0 +1,27 @@
+// Unless explicitly stated otherwise all files in this repository are licensed under the Apache 2.0 License.
+//
+// This product includes software developed at Datadog (https://www.datadoghq.com/). Copyright 2024 Datadog, Inc.
+
+const wt = require('worker_threads')
+
+// Do not want this running on loader thread
+if (!wt.isMainThread) return
+
+const filename = process.argv[1]
+process.env.IITM_TEST_FILE = filename
+
+const [processMajor, processMinor] = process.versions.node.split('.').map(Number)
+
+const match = filename.match(/v([0-9]+)(?:\.([0-9]+))?/)
+
+const majorRequirement = match ? match[1] : 0
+const minorRequirement = match && match[2]
+
+if (processMajor < majorRequirement) {
+  console.log(`skipping ${filename} as this is Node.js v${processMajor} and test wants v${majorRequirement}`)
+  process.exit(0)
+}
+if (processMajor <= majorRequirement && processMinor < minorRequirement) {
+  console.log(`skipping ${filename} as this is Node.js v${processMajor}.${processMinor} and test wants >=v${majorRequirement}.${minorRequirement}`)
+  process.exit(0)
+}