quartz/content/notes/Unit testing.md

Unit testing

• divide code into units ⇒ test those units

• consider appropriate scale

  • depends on type of code project as well as language
  • object oriented: classes? methods?
  • procedural: functions? modules?

• test each unit independently

  • frequently
  • often after each commit/push
  • can run tests if parallel
  • may need to build environment in which tests run

0.1 supports useful principles

can support complementary work by team members early discovery of problems can help with documentation and specification

• unit tests can be a form of executable specification
• helps team members understand requirements

0.2 Test environment

consider code that interacts with a database

• you cant let that code write to a real database
• but you want to check that writes were performed

common solution is to create a fake database

• class that mocs database operations
• can also test error handling by returning error codes

mock up the database with a pretend model that returns fixed results to query

• be careful not to mock up data base incorrectly

can be a pre-recorded interaction

0.3 Test life cycle

• set up test environment
• run test code
• check results
• aggregate results into test summary

simple test: run method ⇒ check value tests may chack that code fails appropriately

• crash when expected
• exceptions are generated

0.4 Language support

language may have bilt in testing support

• e.g., Go and Rust have command line tools to run tests

External tools can often work well too

• e.g., java code annotations can mark tests
• java ignores most annotations, but testing tools (JUnit) can use them
• annotations are symbols that begin with @ in source code

we want to distinguish between tests and normal code

• also should support for sqapping in/out mocking code

0.5 JUnit

test classes have a particular filename pattern annotate test methods with @Test other annotations

• @BeforeAll and @BeforeEach (and after)
• @RepeatedTest

JUnit 5 also supports dynamically generated tests

0.6 TestNG

based off JUnit and fixes some it it's problems

• provides control over threading
  • run tests in parallel
  • also tests for parallelism bugs
  • multithreaded code i hard to debug
• data driven testing
• also
  • integration testing
  • end to end testing