test: add events tests for web-sdk (#410)

- added tests based on [spec
PR](open-feature/spec#171)

Signed-off-by: RealAnna <[email protected]>

packages/client/test/client.spec.ts

@@ -426,4 +426,5 @@ describe('Evaluation details structure', () => {
   });
 });
 
-// context tests are not needed?
+
+

packages/client/test/events.spec.ts

@@ -0,0 +1,158 @@
+import {
+  Provider,
+  ProviderEvents,
+  OpenFeatureEventEmitter,
+  OpenFeatureAPI,
+} from '../src';
+
+const ERROR_REASON = 'error';
+const ERROR_CODE = 'MOCKED_ERROR';
+
+const MOCK_PROVIDER = {
+  metadata: {
+    name: 'mock-events',
+  },
+  initialize: jest.fn(() => {
+    return Promise.resolve(undefined);
+  }),
+  events: new OpenFeatureEventEmitter(),
+} as unknown as Provider;
+
+const ERROR_MOCK_PROVIDER = {
+  metadata: {
+    name: 'mock-events-failure',
+  },
+  initialize: jest.fn(() => {
+    return Promise.reject({
+      reason: ERROR_REASON,
+      errorCode: ERROR_CODE,
+    });
+  }),
+  events: new OpenFeatureEventEmitter(),
+} as unknown as Provider;
+
+
+
+describe('Events', () => {
+  // set timeouts short for this suite.
+  jest.setTimeout(1000);
+  let API: OpenFeatureAPI = new (OpenFeatureAPI as any)();
+
+  afterEach(() => {
+    jest.clearAllMocks();
+    API = new (OpenFeatureAPI as any)(); //TODO this hacky thing should be removed with provider mapping: https://github.com/open-feature/js-sdk/issues/421
+  });
+
+  describe('Requirement 5.1.1', () => {
+    it('The provider defines a mechanism for signalling the occurrence of an event`PROVIDER_READY`', (done) => {
+
+      MOCK_PROVIDER.events?.addListener(ProviderEvents.Ready, () => {
+        try {
+          expect(API.providerMetadata.name).toBe(MOCK_PROVIDER.metadata.name);
+          expect(MOCK_PROVIDER.initialize).toHaveBeenCalled();
+          done();
+        } catch (err) {
+          done(err);
+        }
+      });
+      API.setProvider(MOCK_PROVIDER);
+    });
+
+    it('It defines a mechanism for signalling `PROVIDER_ERROR`', (done) => {
+      //make sure an error event is fired when initialize promise reject
+      ERROR_MOCK_PROVIDER.events?.addListener(ProviderEvents.Error, () => {
+        try {
+          expect(API.providerMetadata.name).toBe(ERROR_MOCK_PROVIDER.metadata.name);
+          expect(ERROR_MOCK_PROVIDER.initialize).toHaveBeenCalled();
+          done();
+        } catch (err) {
+          done(err);
+        }
+      });
+      API.setProvider(ERROR_MOCK_PROVIDER);
+    });
+
+  });
+
+  describe('Requirement 5.2.1, 5.2.3, 5.2.4, 5.2.5 ', () => {
+
+    it('If the provider `initialize` function terminates normally, `PROVIDER_READY` handlers MUST run', (done) => {
+      const client = API.getClient();
+      client.addHandler(ProviderEvents.Ready, () => {
+        done();
+      });
+      API.setProvider(MOCK_PROVIDER);
+    });
+
+    it('If the provider `initialize` function terminates abnormally, `PROVIDER_ERROR` handlers MUST run.', (done) => {
+      const client = API.getClient();
+      client.addHandler(ProviderEvents.Error, () => {
+        done();
+      });
+      API.setProvider(ERROR_MOCK_PROVIDER);
+    });
+
+    it('It defines a mechanism for signalling `PROVIDER_CONFIGURATION_CHANGED`', (done) => {
+      const client = API.getClient();
+      client.addHandler(ProviderEvents.ConfigurationChanged, () => {
+        done();
+      });
+      API.setProvider(MOCK_PROVIDER);
+      // emit a change event from the mock provider
+      MOCK_PROVIDER.events?.emit(ProviderEvents.ConfigurationChanged);
+    });
+
+    it('`PROVIDER_READY` handlers added after the provider is already in a ready state MUST run immediately.', (done) => {
+      const client = API.getClient();
+
+      MOCK_PROVIDER.events?.addListener(ProviderEvents.Ready, () => {
+        try {
+          expect(MOCK_PROVIDER.initialize).toHaveBeenCalled();
+          jest.setTimeout(10);
+          let count = 0;
+          client.addHandler(ProviderEvents.Ready, () => {
+            if (count == 0) {
+              count++;
+              done();
+            }
+          });
+        } catch (err) {
+          done(err);
+        }
+      });
+
+      API.setProvider(MOCK_PROVIDER);
+    });
+  });
+
+  describe('Requirement 5.2.6 ', () => {
+    it('Event handlers MUST persist across `provider` changes.', (done) => {
+      const client = API.getClient();
+
+      const myProvider: Provider = {
+        metadata: {
+          name: 'first',
+        },
+        initialize: jest.fn(() => {
+          return Promise.resolve(undefined);
+        }),
+        events: new OpenFeatureEventEmitter(),
+      } as unknown as Provider;
+
+      API.setProvider(myProvider);
+      let counter = 0;
+      client.addHandler(ProviderEvents.Ready, () => {
+        if (API.providerMetadata.name == myProvider.metadata.name) {
+          API.setProvider(MOCK_PROVIDER);
+          counter++;
+        } else {
+          expect(counter).toBeGreaterThan(0);
+          expect(API.providerMetadata.name).toBe(MOCK_PROVIDER.metadata.name);
+          if (counter == 1) {
+            done();
+          }
+        }
+      });
+    });
+  });
+});