Integration Vs. Unit Tests

main.dart

import 'package:test/test.dart';

typedef NumberFunction = int Function(int);

int addTwo(int original) => original + 2;
int multiplyByTwo(int original) => original * 2;
int subtractThree(int original) => original - 3;
int calculate(
  int original,
  NumberFunction addTwo,
  NumberFunction multiplyByTwo,
  NumberFunction subtractThree,
) =>
    subtractThree(
      multiplyByTwo(
        addTwo(original),
      ),
    );

void main() {
  //---------------------------------------------------------------
  // No isolation
  test('Integration test', () {
    expect(calculate(2, addTwo, multiplyByTwo, subtractThree), 5);
    expect(calculate(5, addTwo, multiplyByTwo, subtractThree), 11);
  });
  //---------------------------------------------------------------

  //---------------------------------------------------------------
  //Complete Isolation
  test('Unit Test addTwo', () {
    expect(addTwo(4), 6);
    expect(addTwo(5), 7);
  });

  test('Unit Test subtractThree', () {
    expect(subtractThree(8), 5);
    expect(subtractThree(14), 11);
  });

  test('Unit Test multiplyByTwo', () {
    expect(multiplyByTwo(4), 8);
    expect(multiplyByTwo(7), 14);
  });

  test('Unit Test calculate', () {
    //These are test doubles to isolate the calculate function
    expect(calculate(2, (n) => 6, (n) => 8, (n) => 5), 5);
  });
  //---------------------------------------------------------------
}