.wp-env.json schema: Make the schema more strict and add unit tests

test/integration/wp-env-schema.test.js

@@ -0,0 +1,43 @@
+/**
+ * External dependencies
+ */
+import Ajv from 'ajv-draft-04';
+import glob from 'fast-glob';
+
+/**
+ * Internal dependencies
+ */
+import wpEnvSchema from '../../schemas/json/wp-env.json';
+
+describe( '.wp-env.json schema', () => {
+	const jsonFiles = glob.sync( [ '.wp-env.json' ], { onlyFiles: true } );
+	const ajv = new Ajv( {
+		allowMatchingProperties: true,
+	} );
+
+	test( 'strictly adheres to the draft-04 meta schema', () => {
+		// Use ajv.compile instead of ajv.validateSchema to validate the schema
+		// because validateSchema only checks syntax, whereas, compile checks
+		// if the schema is semantically correct with strict mode.
+		// See https://github.com/ajv-validator/ajv/issues/1434#issuecomment-822982571
+		const result = ajv.compile( wpEnvSchema );
+
+		expect( result.errors ).toBe( null );
+	} );
+
+	test( 'found .wp-env.json files', () => {
+		expect( jsonFiles.length ).toBeGreaterThan( 0 );
+	} );
+
+	test.each( jsonFiles )( 'validates schema for `%s`', ( filepath ) => {
+		// We want to validate the .wp-env.json file using the local schema.
+		const { $schema, ...metadata } = require( filepath );
+
+		// we expect the $schema property to be present in the .wp-env.json file
+		expect( $schema ).toBeTruthy();
+
+		const result = ajv.validate( wpEnvSchema, metadata ) || ajv.errors;
+
+		expect( result ).toBe( true );
+	} );
+} );