How to turn off parallel execution of tests for multi-project builds?

Question

I have a multi-project build with tests in sub-projects and in a parent project. The build is aggregated so that the parent project runs all tests in child projects.

I configured it so that there's no parallel execution of tests in both the sub-projects and the parent project, via

parallelExecution in Test := false

However, I have the nagging feeling that tests that span over multiple projects are ran in parallel. In the case of one of the sub-projects this is a problem because it mutates state in a test database concurrently, leading to the test to fail.

Any ideas as to how to globally switch of parallel execution of tests, between projects?

score 36 · Accepted Answer · answered Aug 10 '12 at 11:13

36

I think you can apply a setting across projects using scope ThisBuild, like

parallelExecution in ThisBuild := false

I don't know if you can combine that with scope Test, but it might not be necessary.

answered Aug 10 '12 at 11:13

0__

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Sorry, I am kinda new to Scala and faced the same problem - where should I put this line? To which file of the project? – kirhgoff Jun 21 '13 at 12:24
The easiest is to put it into `build.sbt` (that file is used even if you have a full configuration in `project/Build.scala`) – 0__ Jun 21 '13 at 12:38
Thanks! I ve figured it myself, too hasty to ask instead of thinking :). Anyway thank you – kirhgoff Jun 21 '13 at 17:51
Anywhere in particular in build.sbt? – annedroiid Jun 16 '16 at 00:46

score 23 · Answer 2 · answered Oct 31 '15 at 21:27

23

To restrict the number of concurrently executing tests in all projects, use:

concurrentRestrictions in Global += Tags.limit(Tags.Test, 1)

See sbt documentation

See discussion

answered Oct 31 '15 at 21:27

lisak

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score 10 · Answer 3 · answered May 11 '18 at 23:13

10

This worked for me in 1.1.0:

Test / parallelExecution := false

answered May 11 '18 at 23:13

xmar

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score 4 · Answer 4 · edited May 23 '17 at 11:47

4

See my answer here How to run subprojects tests (including setup methods) sequentially when testing

There is another way to prevent parallel execution. You can make the test tasks of the different projects depend on each other:

test in Project2 := (test in Project2).dependsOn(test in Project1).value
parallelExecution in Test in Project2 := false

edited May 23 '17 at 11:47

Community

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answered Dec 29 '14 at 14:33

Boris Stumm

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This doesn't work for me: I am getting `References to undefined settings: Project2/*:test from Project2/*:test (/Users/the21st/Work/Project2/build.sbt:36) Did you mean Project2/web-assets-test:test ?` – the21st Jul 21 '15 at 09:34

score 2 · Answer 5 · answered Feb 14 '22 at 22:49

The "modern" (i.e. sbt 1.x) equivalent of disabling parallel execution in Test scope is to add the following to your build.sbt:

Global / concurrentRestrictions += Tags.limit(Tags.Test, 1)

For those not familiar with sbt syntax, in context you want to do something like:

lazy val main = project
  .in(file("."))
  .settings(
    name := "foo",
    // more settings
    // ...
    Global / concurrentRestrictions += Tags.limit(Tags.Test, 1)
  )

From the tags and rules section of sbt docs.

p.s. quite a useful setting for ScalaTest, particularly around setup/teardown logic during database testing. Fixes some quite puzzling non-deterministic errors that you'll ineviitably hit with parallel execution enabled.

This is the solution I was looking for but, interestingly, I did find that it only worked once I had removed the `Test / parallelExecution := false` rule from the sub-projects that were aggregated by the parent. — Andrew Kirk, May 04 '23 at 20:55

score 1 · Answer 6 · edited May 23 '17 at 12:34

1

Another possibility, based on https://stackoverflow.com/a/27068019/1922026, is to define a command alias in the root project:

.settings(addCommandAlias("test", ";s1/test;s2/test;s3/test"): _*)

where s1, s2 and s3 are the sub-projects. When you are in root project and run "test" the tests will be executed sequentially and in the order defined.

edited May 23 '17 at 12:34

Community

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answered Apr 13 '17 at 14:44

brunovianarezende

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score 1 · Answer 7 · answered Nov 23 '21 at 13:02

1

You can try also Global / parallelExecution := false

answered Nov 23 '21 at 13:02

Alex Elkin

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How to turn off parallel execution of tests for multi-project builds?

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