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Arrange - Act - Assert
public void MyTest() {
// Arrange - Only setup code needed by the act step
// Act - Only the action(s) under test
// Assert - Verification of the excepted behavior
}
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Tip: If any of these parts are greatly bigger than the others, look for refactoring your tests.
Test Class Organization
class SubjectTests {
// fields
int callCount = 0;
// help methods
private Subject MakeSubject() =>
new Subject();
// test methods
public void Test1() { }
public void Test2() { }
public void Test3() { }
}
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This is just a convention. Don't leave help methods and field scattered all around the test methods.
Solitary vs Sociable
Solitary
Type of test that tests a unit without the involvement of other units.
Mocks all dependencies of the subject under test. |
Sociable
Type of test that uses multiple units to verify a given behavior.
Mock only hard to manage dependencies. (e.g. external resources) |
source: Working Effectively with Unit Tests by Jay Fields
Unit-Test
We have control over all it's parts. |
Runs in any order. |
Doesn't depend on another test. |
Doesn't produce side-effects. |
Asserts observable behavior. |
Tip: if any of these is false then it's not a unit-test.
Test - What's your name?
// Convention #1
public void Creating_a_user_stores_it_in_the_database() { ... }
public void Creating_a_user_without_name_throws_exception() { ... }
// Convention #2
public void CreateUser_StoresInDatabase() { ... }
public void CreateUser_WithoutName_ThrowsException() { ... }
// Convention #3
public void Given_user_when_creating_then_its_stored_in_database() { ... }
public void Given_user_when_has_no_name_then_throws_exception() { ... }
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The name of the test should have 3 parts:
- The behavior under test;
- The constraints;
- The expected behavior.
Actions on Loops
public void Test1() {
for(var x in listOfInt) {
Assert.That(GetValue(x), Is.True));
}
}
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Tip: Multiple asserts and action taken within a loop on the same test makes us ignore some cases in case of a failure.
Avoid some Expectations
// Thats how it's done
mock.Verify(...) |
// If possible use specific value, is int.MaxValue a valid expectation?
Assert.That(x, Is.GreaterThan(10)) |
// Might be null
var result = GetObject();
Assert.That(result.Property, Is.True)) |
// Might throw exception somewhere other than action
[ExpectException()] |
// Look for content not types
Assert.IsInstanceOfType(result, typeof(SomeDataModel)); |
Don't ignore the signs!
Sign |
Outcome |
A big arrange section: large dto, many parameters or many mocks. |
Subject under test might be doing to much. |
Tests to data model object (dto). |
Reveals missing tests. DTOs will get their coverage from usage. |
Tests to Exceptions. |
Reveals missing tests. Exceptions will be tested by their usage. |
Big test file |
Can indicate duplication or the subject under test is doing to much. |
Json, xml, etc |
Formatted strings of any kind reveal coupling. Except tests to formatters. |
Big file : Any file greater than 500 lines
Big section : More than 10 lines.
Many parameters : More than 3.
Many Mocks : More than 3.
Large dto: More than 10 properties.
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Parameterized (NUnit)
[Test]
public void Test1([Values(1, 2, 3)] int value) { }
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Parameterized (xUnit)
[Theory]
[InlineData(1)]
[InlineData(2)]
[InlineData(3)]
public void Test1(int value) { }
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Parameterized (MS Tests v2)
[DataTestMethod]
[DataRow(1)]
[DataRow(2)]
[DataRow(3)]
public void Test1(int value) { }
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Isolate - Shared data
static int value = 0;
public void Test1() {
value = 10;
doSomething(value);
}
public void Test2() {
doSomething(value);
}
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Static mutable state will eventually kill one or more tests.
Isolation - Thread safe tests
static object lockObject = new object();
public void Test1() {
lock(lockObject) {
// thread safe code
}
}
public void Test2() {
lock(lockObject) {
// thread safe code
}
}
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Avoid this! Dealing with thread safety in tests adds another layer of complexity.
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