Gradle not running tests

You're saying that the main SourceSet should contain the test directory. This directory should be set in the test SourceSet.

A note for people using Junit5, we need to include the below to enable it - that is, running junit5 tests is not enabled by default.

test {
  useJUnitPlatform()
}

Replace sourceSets with below simple snippet:

sourceSets.main.java.srcDirs = ['src']
sourceSets.test.java.srcDirs = ['tst']