docs/testing/android_instrumentation_tests.md

# Android Instrumentation Tests

Instrumentation tests are JUnit 4 tests that run on devices or emulators. They
can be either unit tests or integration test.

[TOC]

## Unit vs Integration Tests

**When the code under test is library-like code**, mainly defined by its
contract, intended to be used in many contexts, internally complex, and related
bugs are more likely to be introduced to the logic inside it than due to
interactions with other code, **write unit tests**. Unit tests are mostly
Robolectric (`junit` build targets), but some are Instrumentation tests
(`unit_device_javatests` build targets).

**When the code under test is application-like code**, mainly defined by its
behavior, intended to be used in a small number of contexts (often only one),
internally simple, and related bugs are more likely to be in how/when it is
called or due to interactions with other code rather its internal business
logic, **write integration tests**. Integration tests are all Instrumentation
tests (`javatests` build targets).

## Robolectric (workstation) vs Instrumentation (on-device) Tests

When a unit test doesn't require rendering or interacting with the native
library, Robolectric tests, which run on workstations, are preferable to
instrumentation tests, which run on devices and emulators. Robolectric tests are
faster to compile and run.

See [android_robolectric_tests.md] for more info on Robolectric tests.

For integration app-like tests, use an Instrumentation test.

Where supported, use the existing [Transit
Layer](https://source.chromium.org/chromium/chromium/src/+/main:chrome/test/android/javatests/src/org/chromium/chrome/test/transit)
to navigate through the app.

Where not supported yet, expand the Transit Layer by defining the expected app
behavior. See the
[Public Transit README.md](/base/test/android/javatests/src/org/chromium/base/test/transit/README.md)
and follow examples in the Transit Layer.

## Examples of Instrumentation Tests

* Instrumentation Integration test example:
  [ExampleFreshCtaTest](/chrome/android/javatests/src/org/chromium/chrome/browser/ExampleFreshCtaTest.java)
* Instrumentation Unit test example:
  [ExampleOnDeviceUnitTest](/chrome/android/javatests/src/org/chromium/chrome/browser/ExampleOnDeviceUnitTest.java)

## Tracing

Enabling tracing during a test run allows all the function calls involved to be
observed in a visual display (using Chrome's built-in chrome://tracing feature).
To run a test with tracing, add the `--trace-output` flag to the command used to
call the instrumentation test (either running the test_runner.py script, or a
generated binary such as `run_chrome_public_test_apk`). The `--trace-output`
flag takes a filename, which, after the test run, will contain a JSON file
readable by chrome://tracing.

By default, the trace includes only certain function calls important to the test
run, both within the Python test runner framework and the Java code running on
the device. For a more detailed look, add the (no-argument) `--trace-all` flag.
This causes every function called on the Python side to be added to the trace.

## Test Batching Annotations

In Robolectric, all tests are effectively batched.

For Instrumentation tests, see [batching_instrumentation_tests.md] or the summary below:

The
[`@Batch`](https://chromium.googlesource.com/chromium/src/+/main/base/test/android/javatests/src/org/chromium/base/test/util/Batch.java)
annotation is used to run all tests with the same batch group name in the same
instrumentation invocation. In other words, the browser process is not restarted
between these tests, and so most changes to global state, like launching an
Activity, may persist between tests within a batch group. The benefit of this is
that these tests run significantly faster - the per-test cost of restarting the
process can be as high as 10 seconds (usually around 2 seconds), and that
doesn't count the cost of starting an Activity like ChromeTabbedActivity.

## Size Annotations

Size annotations are [used by the test runner] to determine the length of time
to wait before considering a test hung (i.e., its timeout duration), however the
limits aren't very different currently because all tests get a 60s timeout
added.

Annotations from `androidx.test.filters`:

 - [`@SmallTest`](https://developer.android.com/reference/androidx/test/filters/SmallTest.html) (timeout: **10 (+60) seconds**)
 - [`@MediumTest`](https://developer.android.com/reference/androidx/test/filters/MediumTest.html) (timeout: **30 (+60) seconds**)
 - [`@LargeTest`](https://developer.android.com/reference/androidx/test/filters/LargeTest.html) (timeout: **2 (+1) minutes**)

Annotations from `//base`:

 - [`@EnormousTest`](https://chromium.googlesource.com/chromium/src/+/main/base/test/android/javatests/src/org/chromium/base/test/util/EnormousTest.java)
(timeout: **5 (+1) minutes**) Typically used for tests that require WiFi.
 - [`@IntegrationTest`](https://chromium.googlesource.com/chromium/src/+/main/base/test/android/javatests/src/org/chromium/base/test/util/IntegrationTest.java)
(timeout: **10 (+1) minutes**) Used for tests that run against real services.
 - [`@Manual`](https://chromium.googlesource.com/chromium/src/+/main/base/test/android/javatests/src/org/chromium/base/test/util/Manual.java)
(timeout: **10 hours**) Used for manual tests.

[used by the test runner]: https://source.chromium.org/search?q=file:local_device_instrumentation_test_run.py%20symbol:TIMEOUT_ANNOTATIONS&sq=&ss=chromium

## Annotations that Disable Tests

There are several annotations that control whether or not a test runs.
Some are conditional, others are not.

### Unconditional Disabling

[**@DisabledTest**](https://chromium.googlesource.com/chromium/src/+/main/base/test/android/javatests/src/org/chromium/base/test/util/DisabledTest.java)
unconditionally disables a test.
```java
@DisabledTest(
    // Describes why the test is disabled. Typically includes a crbug link.
    message = ""
)
```

### Conditional Disabling

There are two primary annotation categories that conditionally disable tests:
**@DisableIf** and **@Restriction**. The **@DisableIf** annotations are intended
to temporarily disable a test in certain scenarios where it *should* work but
doesn't. In contrast, the **@Restriction** annotation is intended to
permanently limit a test to specific configurations. It signifies that the test
was not, is not, and will not be intended to run beyond those configurations.
In both cases, conditional disabling manifests as a skipped test.

[**@DisableIf.Build**](https://chromium.googlesource.com/chromium/src/+/main/base/test/android/javatests/src/org/chromium/base/test/util/DisableIf.java#25)
allows for conditional test disabling based on values in
[`android.os.Build`](https://developer.android.com/reference/android/os/Build.html):

```java
@DisableIf.Build(

    // Describes why the test is disabled.
    message = "",

    // Disables the test on SDK levels that match the given conditions.
    // Checks against Build.VERSION.SDK_INT.
    sdk_is_greater_than = 0,
    sdk_is_less_than = Integer.MAX_VALUE,

    // Disables the test on devices that support the given ABI
    // (e.g. "arm64-v8a"). Checks against:
    //  - Build.SUPPORTED_ABIS on L+
    //  - Build.CPU_ABI and Build.CPU_ABI2 otherwise
    supported_abis_includes = "",

    // Disables the test on devices with hardware that matches the given
    // value. Checks against Build.HARDWARE.
    hardware_is = "",

    // Disables the test on devices with product names that contain the
    // given value. Checks against Build.PRODUCT.
    product_name_includes = "",

)
```

[**@DisableIf.Device**](https://chromium.googlesource.com/chromium/src/+/main/base/test/android/javatests/src/org/chromium/base/test/util/DisableIf.java#40)
allows for conditional test disabling based on whether
a device is a phone, a tablet, or a "large tablet" as determined by
[org.chromium.ui.base.DeviceFormFactor](https://chromium.googlesource.com/chromium/src/+/main/ui/android/java/src/org/chromium/ui/base/DeviceFormFactor.java).
This is available to tests in
[//ui](https://chromium.googlesource.com/chromium/src/+/main/ui/)
or code that uses //ui.

```java
@DisableIf.Device(
    // Disables the test on devices that match the given type(s) as described
    // above.
    type = {}
)
```

[**@Restriction**](https://chromium.googlesource.com/chromium/src/+/main/base/test/android/javatests/src/org/chromium/base/test/util/Restriction.java)
currently allows for conditional test disabling based on device
type, device performance, internet connectivity, whether Google Play Services is
up to date, and whether the build was an official one.

```java
@Restriction(
    // Possible values include:
    //
    // base:
    //  - Restriction.RESTRICTION_TYPE_LOW_END_DEVICE
    //    Restricts the test to low-end devices as determined by SysUtils.isLowEndDevice().
    //
    //  - Restriction.RESTRICTION_TYPE_NON_LOW_END_DEVICE
    //    Restricts the test to non-low-end devices as determined by SysUtils.isLowEndDevice().
    //
    //  - Restriction.RESTRICTION_TYPE_INTERNET
    //    Restricts the test to devices that have an internet connection.
    //
    // chrome:
    //  - ChromeRestriction.RESTRICTION_TYPE_GOOGLE_PLAY_SERVICES
    //    Restricts the test to devices with up-to-date versions of Google Play Services.
    //
    //  - ChromeRestriction.RESTRICTION_TYPE_OFFICIAL_BUILD
    //    Restricts the test to official builds as determined by ChromeVersionInfo.isOfficialBuild().
    //
    // ui:
    //  - UiRestriction.RESTRICTION_TYPE_PHONE
    //    Restricts the test to phones as determined by DeviceFormFactor.
    //
    //  - UiRestriction.RESTRICTION_TYPE_TABLET
    //    Restricts the test to tablets as determined by DeviceFormFactor.
    value = {}
)
```

[**@MinAndroidSdkLevel**](https://chromium.googlesource.com/chromium/src/+/main/base/test/android/javatests/src/org/chromium/base/test/util/MinAndroidSdkLevel.java)
is similar to **@Restriction** in purpose in that it's
intended to permanently limit a test to only recent versions of Android.

```java
@MinAndroidSdkLevel(
    // The minimum SDK level at which this test should be executed. Checks
    // against Build.VERSION.SDK_INT.
    value = 0
)
```

## Command-Line Flags Annotations

Several annotations affect how a test is run in interesting or nontrivial ways.

[**@CommandLineFlags.Add**](https://chromium.googlesource.com/chromium/src/+/main/base/test/android/javatests/src/org/chromium/base/test/util/CommandLineFlags.java#46)
and
[**@CommandLineFlags.Remove**](https://chromium.googlesource.com/chromium/src/+/main/base/test/android/javatests/src/org/chromium/base/test/util/CommandLineFlags.java#58)
manipulate Chrome's
command-line flags on a per-test basis (i.e., the flags handled by
[`org.chromium.base.CommandLine`](https://chromium.googlesource.com/chromium/src/+/main/base/android/java/src/org/chromium/base/CommandLine.java) and
[`base::CommandLine`](https://chromium.googlesource.com/chromium/src/+/main/base/command_line.h)).

```java
@CommandLineFlags.Add(
    // The flags to add to the command line for this test. These can be
    // anything and typically should include the leading dashes (e.g. "--foo").
    value = {}
)

@CommandLineFlags.Remove(
    // The flags to remove from the command line for this test. These can only
    // be flags added via @CommandLineFlags.Add. Flags already present in the
    // command-line file on the device are only present in the native
    // CommandLine object and cannot be manipulated.
    value = {}
)
```

## Feature Annotations

[**@Feature**](https://chromium.googlesource.com/chromium/src/+/main/base/test/android/javatests/src/org/chromium/base/test/util/Feature.java)
has been used inconsistently in Chromium to group tests across
test cases according to the feature they're testing.

```java
@Feature(
    // The features associated with this test. These can be anything.
    value = {}
)
```

@Feature doesn't have an inherent function, but it can be used to filter tests
via the test runner's
`-A/--annotation` and `-E/--exclude-annotation` flags. For example, this would
run only the tests with @Feature annotations containing at least "Sync" in
`chrome_public_test_apk`:

```bash
out/Debug/bin/run_chrome_public_test_apk -A Feature=Sync
```