chore: add missing test when failing to enhance schema (#15)

src/manifest/__tests__/__mocks__/json-schema-traverse.ts

@@ -0,0 +1,4 @@
+import traverse from 'json-schema-traverse';
+
+// note: it's similar as `jest.spyOn`, but as workaround for default exports
+export default jest.fn(traverse);

src/manifest/__tests__/schema.test.ts

@@ -1,7 +1,11 @@
 import * as xdl from '@expo/xdl/build/project/ExpSchema';
+import traverse, { TraverseCallback } from 'json-schema-traverse';
 import * as schema from '../schema';
 import * as tools from '../../../test/tools';
 
+// note: this is the same value as `traverse`, but typed as mock
+const mockedTraverse = (traverse as unknown) as jest.Mock<[object, TraverseCallback]>;
+
 describe('getSchema', () => {
 	it('fetches schema by expo sdk version', async () => {
 		const xdlSchema = tools.getFixtureFile('schema-xdl-39.0.0.json');
@@ -15,13 +19,17 @@ describe('getSchema', () => {
 
 describe('createFromXdl', () => {
 	const xdlSchema = tools.getFixtureFile('schema-xdl-39.0.0.json');
-	// const simpleSchema = tools.getFixtureFile('schema-plugin-39.0.0.json');
+	const simpleSchema = tools.getFixtureFile('schema-plugin-39.0.0.json');
 	const enhancedSchema = tools.getFixtureFile('schema-enhanced-39.0.0.json');
 
 	it('creates enhanced plugin schema from xdl', () => {
 		const createdSchema = schema.createFromXdl('39.0.0', xdlSchema);
 		expect(createdSchema).toStrictEqual(expect.objectContaining(enhancedSchema));
 	});
 
-	// todo: add test to validate it falls back to original schema
+	it('uses simple plugin schema when failing to enhance', () => {
+		mockedTraverse.mockImplementationOnce(() => { throw new Error('Failed traversing schema'); });
+		const createdSchema = schema.createFromXdl('39.0.0', xdlSchema);
+		expect(createdSchema).toStrictEqual(expect.objectContaining(simpleSchema));
+	});
 });