# CTest: build dependency as test fixture
**URL:** https://discourse.cmake.org/t/ctest-build-dependency-as-test-fixture/15169
**Category:** Development
**Created:** [September 16, 2025, 2:28pm UTC](https://discourse.cmake.org/t/ctest-build-dependency-as-test-fixture/15169 "2025-09-16T14:28:18Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@purpleKarrot](https://discourse.cmake.org/u/purpleKarrot)
#### Post date: [September 16, 2025, 2:28pm UTC](https://discourse.cmake.org/t/ctest-build-dependency-as-test-fixture/15169/1 "2025-09-16T14:28:18Z")
The following code defines a test executable and two tests:
```cmake
add_executable(foo_test ...)
add_test(NAME foo.test.1 COMMAND foo_test -1)
add_test(NAME foo.test.2 COMMAND foo_test -2)
```
With `CMAKE_SKIP_TEST_ALL_DEPENDENCY` set to `OFF`, running `make test` will build the test executable before running the tests, unless `EXCLUDE_FROM_ALL` is set as a target or directory property. Running `ctest` directly will not build the test executable at all.
I’d like to discuss an alternative approach that would build the test executable before running the tests that rely on it, whether the tests are launched through `ctest` or `make test` and whether `EXCLUDE_FROM_ALL` is set or not:
If the test command is an executable target, then (based on some variable or property that is yet to be determined) a test fixture is implicitly defined and added as a requirement of the test.
That means, the code
```cmake
set(CMAKE_COME_UP_WITH_REASONABLE_NAME ON)
add_executable(foo_test ...)
add_test(NAME foo.test.1 COMMAND foo_test -1)
add_test(NAME foo.test.2 COMMAND foo_test -2)
```
would behave like
```cmake
add_executable(foo_test ...)
add_test(NAME foo.test.1 COMMAND foo_test -1)
add_test(NAME foo.test.2 COMMAND foo_test -2)
add_test(NAME cmake_build.foo_test
COMMAND "${CMAKE_COMMAND}"
--build "${CMAKE_BINARY_DIR}"
--config $
--target foo_test
)
set_tests_properties(cmake_build.foo_test PROPERTIES
FIXTURES_SETUP cmake_build.foo_test
)
set_tests_properties(foo.test.1 PROPERTIES
FIXTURES_REQUIRED cmake_build.foo_test
)
set_tests_properties(foo.test.2 PROPERTIES
FIXTURES_REQUIRED cmake_build.foo_test
)
```
---
### Author:  [@craig.scott](https://discourse.cmake.org/u/craig.scott)
#### Post date: [September 17, 2025, 1:33pm UTC](https://discourse.cmake.org/t/ctest-build-dependency-as-test-fixture/15169/2 "2025-09-17T13:33:52Z")
If you try to run a build as part of (or a setup step for) a test, you can no longer run any tests in parallel. You would potentially end up with multiple builds running at the same time for the same build directory.
I don’t think we should be supporting doing a build in the main project’s build directory as part of running tests.
If your proposal is to work out all required targets if the user builds the `test` target, that’s a different scenario. Personally I think we should be trying to direct users to run `ctest` directly rather than building the `test` target though, and I think trying to build required targets as part of the `test` target will more often than not be not much different to building the default `all` target. I get it that there will be cases where this is not true, but for the effort involved in implementing it, the value seems questionable (to me, I’m happy to be wrong though if someone else wants to expend that time and effort).
---
### Author:  [@purpleKarrot](https://discourse.cmake.org/u/purpleKarrot)
#### Post date: [September 18, 2025, 8:04am UTC](https://discourse.cmake.org/t/ctest-build-dependency-as-test-fixture/15169/3 "2025-09-18T08:04:04Z")
> [@craig.scott](#):
>
> You would potentially end up with multiple builds running at the same time for the same build directory.
>
> I don’t think we should be supporting doing a build in the main project’s build directory as part of running tests.
Yes, that is convincing.
> I think trying to build required targets as part of the `test` target will more often than not be not much different to building the default `all` target.
Consider the following usecase:
```cmake
block()
set(BUILD_SHARED_LIBS OFF)
add_subdirectory(bar EXCLUDE_FROM_ALL)
endblock()
add_library(foo)
target_link_libraries(foo PRIVATE bar::bar)
```
We want to build a third party library as STATIC, irrespective of the setting of `BUILD_SHARED_LIBS` in the main project. We don’t want to build other parts of the third party project and we especially want to exclude third party components from being installed, hence the `EXCLUDE_FROM_ALL`.
But now we have a situation where the `all` target does not build all required targets for testing.
The [EXCLUDE\_FROM\_ALL](https://cmake.org/cmake/help/git-master/prop_dir/EXCLUDE_FROM_ALL.html) **directory** property has this exception:
> If a target built by the parent project depends on a target in the subdirectory, the dependee target will be included in the parent project build system to satisfy the dependency.
Do we need another exception for executable targets that are used as the `COMMAND` in [`add_test`](https://cmake.org/cmake/help/git-master/command/add_test.html) to satisfy the testing dependency? That command already has three special cases when the command is an executable target. Something like:
> If `` specifies an executable target created by [`add_executable()`](https://cmake.org/cmake/help/git-master/command/add_executable.html#command:add_executable):
>
> -
> -
> -
> - **Add:** the exectuable target is included in the `ALL` target.