Yyds dry inventory what is test driven development

Definition

Test-driven development , English name Test-driven development, It's about a programming style .

There are mainly three processes closely intertwined ：

• code
• test （ In the form of writing unit tests ）
• Design （ In the form of refactoring ）

It can be succinctly described by the following set of rules ：

• Write a unit test , To describe one aspect of the program
• Run the test , If the program lacks functions, it will fail
• To write “ Adequate ” Code for , As simple as possible , To make the test pass
• “ Refactoring code ”, Until it meets the simplicity criteria
• repeat , as time goes on “ The accumulation of ” unit testing

Expected revenue

If you do this, you may reap benefits ：

• Team code bug A significant reduction in the rate , But the code is a modest increase in the initial development work
• The same team reported that these indirect costs were offset by a reduction in work at the final stage of the project
• Although empirical studies so far have failed to confirm this , But senior practitioners report ,TDD It can improve the design quality in the code , And more generally improve “ Inside ” Or technical quality , For example, improve the indicators of cohesion and coupling

Common pitfalls

Typical personal mistakes include ：

• Forget to run tests often
• Write too many tests at once
• Write tests that are too large or too coarse
• Write too trivial tests , For example, omit assertions
• Write tests for trivial code , For example, accessors

Typical team misconceptions include ：

• Partial use of —— Only a few developers on the team use TDD
• The test suite is poorly maintained -- The most common reason is that the test suite runs too long
• Obsolete test suite （ That is, it rarely or never runs ）-- Sometimes due to poor maintenance , Sometimes it is caused by the flow of team personnel

origin

Although the idea of testing and refinement before programming is not the original idea of the agile community , but TDD Constitutes a breakthrough , Because it combines this idea with “ Developer testing ” The idea of combining , It provides new respect for developer testing .

• 1976 year ：Glenford Myers Published “ Software reliability ”, Which point out that “ Developers should not test their own code ” Of “ axiom ”（ The dark age of developer testing ）
• 1990： With “ Black box ” Technology based testing discipline , Especially with “ Capture and playback ” Form of test tool
• 1991 year ： stay Taligent Independently created a testing framework , And SUnit There are amazing similarities （ source ：SUnit）.
• 1994 year ：Kent Beck by Smalltalk Write the SUnit The test framework （ source ）
• 1998： The article about extreme programming mentioned “ We usually write tests first ”（ source ）
• 1998 Year to 2002 year ：“Test First” Elaborated as “Test Driven”, Especially in C2.com Wiki On
• 2000： Simulation object is one of the new technologies developed in that period （ source ）
• 2003 year ：Kent Beck Published “ Test-driven development ： Example ”

To 2006 year ,TDD It is already a relatively mature discipline , It has begun to encourage further innovation derived from it , Such as ATDD or BDD）.

The logo used

• “ Code coverage ” Is to prove the use of TDD The common method of ; Although high coverage does not guarantee correct use TDD, But lower than 80% Coverage of may indicate that the team is interested in TDD Insufficient mastery of
• The version control log should show that the test code is checked in every time the product code is checked in , The quantity is roughly the same

Technical level

beginner

• Be able to write a unit test before writing the corresponding code
• Be able to rewrite code enough to pass failed tests

intermediate

• practice “ Test driven bug fixes ”： When defects are found , Write a test that exposes defects before correcting
• It can decompose the characteristics of a composite program into several unit test sequences to write
• Know and be able to say some strategies to guide the writing of tests （ for example ," When testing a recursive algorithm , First write a test for recursive termination "）.
• Be able to find reusable elements from existing unit tests , Test tools that generate specific situations

senior

• Be able to develop planned unit tests for macro features " The roadmap "（ And modify it if necessary ）
• can " Test drive " Various design paradigms ： object-oriented 、 Functionalization 、 Event driven
• can " Test drive " Various technical fields ： Calculation 、 The user interface 、 Persistent data access .......

Extended reading

​ ​Test Driven Development: By Example​​, by Kent Beck

Link to the original text ：https://www.agilealliance.org/glossary/tdd/#q=~(infinite~false~filters~(postType~(~'page~'post~'aa_book~'aa_event_session~'aa_experience_report~'aa_glossary~'aa_research_paper~'aa_video)~tags~(~'tdd))~searchTerm~'~sort~false~sortDirection~'asc~page~1)