Inappropriate usage of t.Parallel() method GO-W6007
Bug risk
Critical
Using the t.Parallel() method can be tricky and ollowing are some common inappropriate
usages of t.Parallel:
— t.Parallel() is called in either a top-level test function or a sub-test function only
— t.Parallel() is called in the sub-test function; it is post-processed by defer instead of t.Cleanup()
Here's a good blog post explaining how t.Parallel should be used.
The description of the Parallel() method from Go's official documentation:
func (t *T) Parallel()
Parallel signals that this test is to be run in parallel with (and only
with) other parallel tests. When a test is run multiple times due to use of
-test.count or -test.cpu, multiple instances of a single test never run in
parallel with each other.
Bad practice
func Test_TB2(t *testing.T) {
teardown := setup("Test_TB2")
t.Cleanup(teardown)
t.Parallel() // "Test_TB2's subtests should call t.Parallel"
tests := []struct { name string }{
{ name: "TB2_Sub1" },
{ name: "TB2_Sub2" },
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
call(tt.name)
})
}
}
func Test_Func1(t *testing.T) {
teardown := setup("Test_Func1")
t.Cleanup(teardown)
// "Test_Func1 should call t.Parallel on the top level as well"
t.Run("Func1_Sub1", func(t *testing.T) {
call("Func1_Sub1")
t.Parallel()
})
t.Run("Func1_Sub2", func(t *testing.T) {
call("Func1_Sub2")
t.Parallel()
})
}
Recommended
func Test_TB2(t *testing.T) {
teardown := setup("Test_TB2")
t.Cleanup(teardown)
t.Parallel()
tests := []struct { name string }{
{ name: "TB2_Sub1" },
{ name: "TB2_Sub2" },
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
t.Parallel()
call(tt.name)
})
}
}
func Test_Func1(t *testing.T) {
teardown := setup("Test_Func1")
t.Cleanup(teardown)
t.Parallel()
t.Run("Func1_Sub1", func(t *testing.T) {
call("Func1_Sub1")
t.Parallel()
})
t.Run("Func1_Sub2", func(t *testing.T) {
call("Func1_Sub2")
t.Parallel()
})
}