add test case for enum validation

lib/WebpackOptionsValidationError.js

@@ -154,6 +154,10 @@ class WebpackOptionsValidationError extends WebpackError {
 				return "RegExp";
 		}
 
+		if (schema.enum) {
+			return schema.enum.map(item => JSON.stringify(item)).join(" | ");
+		}
+
 		if (schema.$ref) {
 			return formatInnerSchema(getSchemaPart(schema.$ref), true);
 		}
@@ -166,9 +170,6 @@ class WebpackOptionsValidationError extends WebpackError {
 		if (schema.anyOf) {
 			return schema.anyOf.map(formatInnerSchema).join(" | ");
 		}
-		if (schema.enum) {
-			return schema.enum.map(item => JSON.stringify(item)).join(" | ");
-		}
 		return JSON.stringify(schema, null, 2);
 	}
 
@@ -250,6 +251,7 @@ class WebpackOptionsValidationError extends WebpackError {
 				err.parentSchema
 			)}`;
 		} else if (err.keyword === "enum") {
+			console.log(err.parentSchema);
 			if (
 				err.parentSchema &&
 				err.parentSchema.enum &&

test/Validation.test.js

@@ -458,6 +458,20 @@ describe("Validation", () => {
       -> The run point of the plugin, required method.
     * configuration.plugins[0] should be an instance of function
       -> Function acting as plugin"
+`)
+	);
+
+	createTestCase(
+		"invalid mode",
+		{
+			mode: "protuction"
+		},
+		msg =>
+			expect(msg).toMatchInlineSnapshot(`
+"Invalid configuration object. Webpack has been initialised using a configuration object that does not match the API schema.
+ - configuration.mode should be one of these:
+   \\"development\\" | \\"production\\" | \\"none\\"
+   -> Enable production optimizations or development hints."
 `)
 	);
 });