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Programming in D: The Ultimate Guide for Software Engineers

Test-Driven Development

This lesson explains a software development methodology that focuses on unit testing.

We'll cover the following...

Test-driven development

Test-driven development (TDD) is a software development methodology that prescribes writing unit tests before implementing functionality. In TDD, the focus is on unit testing. Coding is a secondary activity that makes the tests pass.
In accordance with TDD, the ordinal() function below can first be implemented intentionally incorrectly:

D
import std.string;
string ordinal(size_t number) {
    return "";    // ← intentionally wrong
}
unittest {
    assert(ordinal(1) == "1st");
    assert(ordinal(2) == "2nd");
    assert(ordinal(3) == "3rd");
    assert(ordinal(10) == "10th");
}
void main() {
}

The function should ...