Component tests

<<../../../_common/components/_tests_intro.md>>

Test runners

Test runners are reusable adapters between the Test Runner Framework and common frameworks used by developers to write tests in their preferred language. Each test runner component exposes the fuchsia.test.Suite capability that enables the test_manager to enumerate and execute individual tests, and declares the appropriate execution runner with test framework support.

{
    // Execute tests using language-specific runner
    program: { runner: "elf_test_runner", },
    // Expose test suite protocol to test manager
    capabilities: [
        { protocol: "fuchsia.test.Suite" },
    ],
    expose: [
        {
            protocol: "fuchsia.test.Suite",
            from: "self",
        },
    ],
}

To simplify integration, the Test Runner Framework provides manifest shards for each language-specific runner. The following is an equivalent test runner CML for declaring the capabilities from the previous example component tests.

{
    include: [ "sys/testing/elf_test_runner.shard.cml" ]
}

Note: For complete details on the Test Runner Framework and component testing, see the testing documentation.

Unit tests

Unit testing{:.external} focuses on validating the individual units of code within your component and isolated from other components on the system. Unit tests should be hermetic, meaning that they do not require or provide additional capabilities outside of the test.

The Fuchsia SDK provides additional templates to facilitate unit testing components:

• cc_test(): Compiles the C++ source code into a test binary.
• fuchsia_test_component(): Generates a Fuchsia component containing tests. You can combine multiple test components into the same fuchsia_package().

Below is an example BUILD.bazel snippet for including unit tests:

load(
    "fuchsia_cc_binary",
    "fuchsia_package",
    "fuchsia_test_component",
)

cc_test(
    name = "hello_world_test",
    srcs = [
        "hello_world_test.cc",
    ],
)

fuchsia_test_component(
  name = "unit_test_component",
  test_name = "hello_world_test",
  deps = [
      ":hello_world_test",
  ],
)

fuchsia_package(
    name = "unit_test_pkg",
    visibility = ["//visibility:public"],
    deps = [
      ":unit_test_component",
    ],
)

Exercise: Echo unit tests

In this exercise, you'll add unit tests to the echo component with the Test Runner Framework and run those tests in a FEMU environment.

Implement unit tests

Unit tests verify that the internal functions of the component behave as expected. For the echo component, you'll validate that the greeting() function used in the previous exercise returns the expected values.

Add the following unit test functions to validate the behavior of the greeting() function when supplied with one, two, or three arguments:

echo/echo_unittest.cc:

{% includecode gerrit_repo="fuchsia/sdk-samples/getting-started" gerrit_path="src/echo/echo_unittest.cc" region_tag="imports" adjust_indentation="auto" %}

#include "echo_component.h"

{% includecode gerrit_repo="fuchsia/sdk-samples/getting-started" gerrit_path="src/echo/echo_unittest.cc" region_tag="test_mod" adjust_indentation="auto" %}

Run the unit tests

Add the following to your BUILD.bazel file to include your tests in the build configuration:

BUILD.bazel:

{% includecode gerrit_repo="fuchsia/sdk-samples/getting-started" gerrit_path="src/echo/BUILD.bazel" region_tag="imports" adjust_indentation="auto" %}

# ...

{% includecode gerrit_repo="fuchsia/sdk-samples/getting-started" gerrit_path="src/echo/BUILD.bazel" region_tag="unittest" adjust_indentation="auto" %}

This rule packages your unit tests into a component with the following URL:

fuchsia-pkg://fuchsiasamples.com/echo_unittests#meta/echo_unittests.cm

Run bazel build and verify that the build completes successfully:

bazel build --config=fuchsia_x64 //fuchsia-codelab/echo:test_pkg \
    --publish_to=$HOME/.package_repos/sdk-samples

Use the ffx test command to execute the unit tests inside this package. Verify that the tests pass:

ffx test run \
    fuchsia-pkg://fuchsiasamples.com/echo_unittests#meta/echo_unittests.cm