Add tests for config-normalize helpers, expose internals for testability and documents bugs

src/config-imports.3tg.md

@@ -0,0 +1,40 @@
+# Exported functions from "src/config-imports.ts"
+
+<!--
+```json configuration
+{
+  "testing-framework": "vitest",
+  "no-mock-imports": true
+}
+```
+-->
+
+```json configuration
+{
+  "before-imports": [
+    "// Here we test only `toFileUrl` from `src/config-imports.ts` as",
+    "// `pathsForImport` and `readExternalEntries` should be tested for",
+    "// their corresponding source code files"
+  ]
+}
+```
+
+## toFileUrl(filePath: string)
+
+These are the functional requirements for function `toFileUrl`.
+
+| test name | filePath        | toFileUrl                       |
+| --------- | --------------- | ------------------------------- |
+|           | '/foo'          | 'file:///foo' as any            |
+|           | '/foo#1'        | 'file:///foo%231' as any        |
+|           | '/some/path%.c' | 'file:///some/path%25.c' as any |
+
+We need to use `as any` as the return is of type `URL`, but we'll change the argument for `expect()` so we can compare it with our strings.
+
+```json configuration
+{
+  "expect-values": {
+    "/toFileUrl/": "$$(filePath).href"
+  }
+}
+```