Support choosing channel to download SDK components from.

__tests__/channel-id-mapper.test.ts

@@ -0,0 +1,17 @@
+import * as mapper from '../src/channel-id-mapper';
+
+describe('channel id mapper tests', () => {
+  it('Throws if channelName is unknown', () => {
+    const func = () => {
+      mapper.getChannelId('unknown-channel');
+    };
+    expect(func).toThrowError(`Unexpected channel name: 'unknown-channel'.`);
+  });
+
+  it('Returns expected channelId from channelName', () => {
+    expect(mapper.getChannelId('stable')).toBe(0);
+    expect(mapper.getChannelId('beta')).toBe(1);
+    expect(mapper.getChannelId('dev')).toBe(2);
+    expect(mapper.getChannelId('canary')).toBe(3);
+  });
+});

__tests__/input-validator.test.ts

@@ -102,6 +102,37 @@ describe('arch validator tests', () => {
   });
 });
 
+describe('channel validator tests', () => {
+  it('Throws if channel is unknown', () => {
+    const func = () => {
+      validator.checkChannel('some-channel');
+    };
+    expect(func).toThrowError(`Value for input.channel 'some-channel' is unknown. Supported options: ${validator.VALID_CHANNELS}`);
+  });
+
+  it('Validates successfully with valid channel', () => {
+    const func1 = () => {
+      validator.checkChannel('stable');
+    };
+    expect(func1).not.toThrow();
+
+    const func2 = () => {
+      validator.checkChannel('beta');
+    };
+    expect(func2).not.toThrow();
+
+    const func3 = () => {
+      validator.checkChannel('dev');
+    };
+    expect(func3).not.toThrow();
+
+    const func4 = () => {
+      validator.checkChannel('canary');
+    };
+    expect(func4).not.toThrow();
+  });
+});
+
 describe('force-avd-creation validator tests', () => {
   it('Throws if force-avd-creation is not a boolean', () => {
     const func = () => {