Unit Testing with Google Test in Bazel
Google Test is a well-established framework for unit tests in C++. It provides lots of features and can be used to write tests for own classes and their methods. Its integration in Bazel build system works quite well, with the benefit that it is not necessary to copy Google Test source files into the own repository or use Git submodules, as Google Test’s repository is downloaded on demand by Bazel during the build process. In this blog post, I will describe how REL uses Google Test. This approach can easily be transferred to every C++ development project that uses Bazel as build system.
First of all, Google Test has to be added as external dependency to the Bazel WORKSPACE file. Bazel’s
new_git_repository rule can be used for this.
new_git_repository( name = "googletest", build_file = "gmock.BUILD", remote = "https://github.com/google/googletest", tag = "release-1.10.0", )
In this snippet, Google Test’s public repo on Github is referenced, and a dedicated tag is selected. If there is a new version of Google Test available, it is sufficient to update the tag in this rule, to change the dependency for all unit tests in the workspace.
As a second step, build file
gmock.BUILD is created in folder
external. It contains the Bazel definitions for Google Test, so that the referenced code is available as
cc_library( name = "gtest", srcs = [ "googletest/src/gtest-all.cc", "googlemock/src/gmock-all.cc", ], hdrs = glob([ "**/*.h", "googletest/src/*.cc", "googlemock/src/*.cc", ]), includes = [ "googlemock", "googletest", "googletest/include", "googlemock/include", ], linkopts = ["-pthread"], visibility = ["//visibility:public"], ) cc_library( name = "gtest_main", srcs = ["googlemock/src/gmock_main.cc"], linkopts = ["-pthread"], visibility = ["//visibility:public"], deps = [":gtest"], )
The first library includes all Google Test related source files, whereas the second rule only contains the reference to Google Test’s
Now Google Test is available in the build environment as external dependency. If it is required as part of a build, it is downloaded and built (and cached) by Bazel. To use it for own unittests,
gtest_main rule is referenced as dependency by the
cc_test rule, which also includes the
*Test.cpp - files, which contain the test cases.
cc_test( name = "RelLibUnitTest", srcs = glob(["**/*.cpp"]), deps = [ "//rel-lib:rel_lib", "@googletest//:gtest_main", ], )
cc_test is the “executable”, which brings together the test cases (in this example, added to
srcs), the actual source code that shall be tested (dependency to
rel_lib) and the Google Test Framework, referenced as dependency, too.
To run it,
bazel test //path/to:RelLibUnitTest is executed. Google Test logfiles are not printed out to the command line, they are stored in