Lint banner imports in tests

Enforce importing from the same folder to avoid copy-paste errors,
running tests on old banners.

Ticket: https://phabricator.wikimedia.org/T369276

package.json

@@ -24,6 +24,7 @@
     "lint:js": "eslint --ext .js,.vue,.ts,.cjs --cache --cache-location .eslintcache --ignore-path .gitignore .",
     "lint:ts": "vue-tsc --noEmit",
     "lint:css": "stylelint '**/*.{scss,vue}'",
+    "lint:test-imports": "node test/find_mismatched_imports.mjs",
     "ci": "npm-run-all lint test",
     "check-content-version": "ts-node check-content-version.ts",
     "coverage": "vitest run --coverage",

test/find_mismatched_imports.mjs

@@ -0,0 +1,48 @@
+import fg from 'fast-glob';
+import path from 'path';
+import * as readline from "node:readline";
+import * as fs from "node:fs";
+
+const mismatchedImports = [];
+
+// Find all test files in the banners folder, create a stream to iterate over them
+const stream = fg.stream( 'test/banners/*/**/*.ts' );
+
+// Regular expression to match import statements. We only care about the path part
+// and that it contains the pattern "banners/CHANNEL_NAME/CAMPAIGN_NAME"
+const importRegex = /import .+ from .+(banners\/\w+\/\w+)/;
+
+for await ( const entry of stream ) {
+	// skip thank_you banners, they are not organized by campaign
+	if ( entry.includes( 'test/banners/thank_you' ) ) {
+		continue;
+	}
+
+	// Extract expected path from entry, e.g. "banners/desktop/C24_WMDE_Desktop_01"
+	const pathParts = entry.split( path.sep );
+	// drop "test" prefix
+	pathParts.shift();
+	const expectedPath = pathParts.slice( 0, 3 ).join( path.sep );
+
+	// Check each line of the file for mismatched imports
+	const lineReader = readline.createInterface( {
+		input: fs.createReadStream( entry )
+	} );
+	let lineNumber = 1;
+	for await ( const line of lineReader ) {
+		const match = line.match( importRegex );
+		if( match && !match[1].includes( expectedPath ) ) {
+			mismatchedImports.push( { entry, line, lineNumber } );
+		}
+		lineNumber++;
+	}
+}
+
+if ( mismatchedImports.length === 0 ) {
+	// Don't print anything if there are no mismatches, be a good POSIX citizen
+	process.exit( 0 );
+}
+
+console.log( 'The following banner tests import from the wrong campaign folders:' );
+console.log( mismatchedImports );
+process.exit( 1 );