Cannot run go tests in "main" package in IntellijIdea Ultimate with go plugin

Let's consider the following example with main.go and main_test.go files:

package main

import (
   "log"
)

func main() {
   log.Printf(foo())
}

func foo() string {
   return "Foo"
}

package main

import (
   "testing"
)

func TestFoo(t *testing.T) {
   t.Error(foo())
}

You can start a debug session by setting a breakpoint in main_test.go and click on the gutter icon around TestFoo() function.

Could you please elaborate a bit? Do you get any errors during debug sessions?