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test double

A stand-in for a real dependency, used so a test can run without it.

A test double (fake, stub, or mock) implements the same trait as the real dependency, so code written against the trait can be tested without a network, clock, or disk.

Examples

  • struct FixedClock(u32) implements the same Clock trait as SystemClock, so a test can check overdue(98, &FixedClock(101)) on a day it chooses.

See also

dependency injection integration test trait
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