Initial implementation with unit test.

README.md

@@ -6,6 +6,29 @@
 
 A wrapper around @aws-sdk/client-appconfigdata to provide background polling and caching.
 
+## Usage
+
+Initialize:
+
+```typescript
+const poller = new Poller({
+  dataClient: dataClient,
+  sessionConfig: {
+    ApplicationIdentifier: 'MyApp',
+    EnvironmentIdentifier: 'Test',
+    ConfigurationProfileIdentifier: 'Config1',
+  },
+  logger: console.log,
+});
+
+await poller.start();
+```
+
+Fetch:
+
+```typescript
+const value = poller.getConfigurationString().latestValue;
+```
 
 ## License
 

__tests__/poller.test.ts

@@ -0,0 +1,49 @@
+import { Poller } from '../src/poller.js';
+import {
+  AppConfigDataClient,
+  GetLatestConfigurationCommand,
+  StartConfigurationSessionCommand,
+} from '@aws-sdk/client-appconfigdata';
+import { mockClient } from 'aws-sdk-client-mock';
+import { Uint8ArrayBlobAdapter } from '@smithy/util-stream';
+
+describe('Poller', () => {
+  const appConfigClientMock = mockClient(AppConfigDataClient);
+
+  const configValue = 'Some Configuration';
+
+  appConfigClientMock.on(StartConfigurationSessionCommand).resolves({
+    InitialConfigurationToken: 'initialToken',
+  });
+
+  appConfigClientMock.on(GetLatestConfigurationCommand).resolves({
+    Configuration: Uint8ArrayBlobAdapter.fromString(configValue),
+  });
+
+  const dataClient = new AppConfigDataClient();
+
+  let poller: Poller<string> | undefined;
+
+  afterAll(() => {
+    console.log('Stopping poller');
+    poller.stop();
+  });
+
+  it('Polls', async () => {
+    poller = new Poller({
+      dataClient: dataClient,
+      sessionConfig: {
+        ApplicationIdentifier: 'MyApp',
+        EnvironmentIdentifier: 'Test',
+        ConfigurationProfileIdentifier: 'Config1',
+      },
+      logger: console.log,
+    });
+
+    await poller.start();
+    const latest = poller.getConfigurationString();
+
+    expect(latest.latestValue).toEqual(configValue);
+    expect(latest.errorCausingStaleValue).toBeUndefined();
+  });
+});