Test Structure

Test should follow three steps:

Setup
Method
Validation/Assertion

Boundaries

Avoid implementation of external dependencies in unit tests.

Using things like dependency injection (and shallow-mocking the dependencies), you can avoid relying on the actual implementations to run properly for the test to pass.

// external dependencies and its implementation tested
import (
  someExternalFunction
)

func testTightCoupling(someParam: string) boolean {
  testValue := someParam
  
  // calling actual implementation (bad)
  someExternalFunction(testValue);
  
  // assertion
}

// shallow dependencies using mock return value
const mockedServiceMethod = mock(someExternalFunction)

func testLooseCoupling() boolean {
  testValue := someParam
  
  // calling mocked implementation
  mockedServiceMethod(testValue)
}