Bug 1482150 - Create a unit test to verify all corner cases of the helper method. r=padenot

Quering the stored devices list for an ID was not always correct. The stored devices list is expected to be empty before an enumeration takes place or after a collection change notification. In those cases, the method will fail to find an existing ID. The method has been updated to address these cases in previous patch. Here I have implemented a unit test to verify the case. Currently, the method is not being used.

Differential Revision: https://phabricator.services.mozilla.com/D9380

--HG--
extra : moz-landing-system : lando

dom/media/gtest/TestAudioDeviceEnumerator.cpp

@@ -620,5 +620,45 @@ TEST(CubebDeviceEnumerator, ForceNullCubebContext)
   nsTArray<RefPtr<AudioDeviceInfo>> outputDevices;
   enumerator->EnumerateAudioOutputDevices(outputDevices);
   EXPECT_EQ(outputDevices.Length(), 0u) << "Enumeration must fail, output device list must be empty.";
+
+  // Shutdown to clean up the null context effect
+  CubebDeviceEnumerator::Shutdown();
 }
 
+TEST(CubebDeviceEnumerator, DeviceInfoFromId)
+{
+  MockCubeb* mock = new MockCubeb();
+  mozilla::CubebUtils::ForceSetCubebContext(mock->AsCubebContext());
+
+  uint32_t device_count = 4;
+  cubeb_device_type deviceTypes[2] = {CUBEB_DEVICE_TYPE_INPUT,
+                                     CUBEB_DEVICE_TYPE_OUTPUT};
+
+  bool supportsDeviceChangeCallback[2] = { true, false };
+  for (bool supports : supportsDeviceChangeCallback) {
+    // Shutdown for `supports` to take effect
+    CubebDeviceEnumerator::Shutdown();
+    mock->SetSupportDeviceChangeCallback(supports);
+    for (cubeb_device_type& deviceType : deviceTypes) {
+      AddDevices(mock, device_count, deviceType);
+
+      cubeb_devid id_1 = reinterpret_cast<cubeb_devid>(1);
+      RefPtr<CubebDeviceEnumerator> enumerator = CubebDeviceEnumerator::GetInstance();
+      RefPtr<AudioDeviceInfo> devInfo = enumerator->DeviceInfoFromID(id_1);
+      EXPECT_TRUE(devInfo) << "the device exist";
+      EXPECT_EQ(devInfo->DeviceID(), id_1) << "verify the device";
+
+      mock->RemoveDevice(id_1);
+      devInfo = enumerator->DeviceInfoFromID(id_1);
+      EXPECT_FALSE(devInfo) << "the device does not exist any more";
+
+      cubeb_devid id_5 = reinterpret_cast<cubeb_devid>(5);
+      mock->AddDevice(DeviceTemplate(id_5, deviceType));
+      devInfo = enumerator->DeviceInfoFromID(id_5);
+      EXPECT_TRUE(devInfo) << "newly added device must exist";
+      EXPECT_EQ(devInfo->DeviceID(), id_5) << "verify the device";
+    }
+  }
+  // Shutdown for `supports` to take effect
+  CubebDeviceEnumerator::Shutdown();
+}