TestableAssert

Use TestableAssert to test if assertions in your code can catch programming errors properly

// TestLibrary.swift

func testWithAssert() {
  assert(false, "assert() message")
}

func testWithPreconditionFailure() {
  preconditionFailure("preconditionFailure() message")
}

func testWithFatalError() {
  fatalError("fatalError() message")
}

func testWithRandomFailure() {
  let testFuncs = [
    testWithAssert,
    testWithPreconditionFailure,
    testWithFatalError,
  ]
  guard let testFunc = testFuncs.randomElement() else {
    fatalError()
  }
  
  testFunc()
}

// Tests.swift

expectFailedAssertion({ testWithAssert() })
expectFailedPrecondition({ testWithPreconditionFailure() }, "preconditionFailure() message")
expectFatalError({ testWithFatalError() })
expectAnyFailure({ testWithRandomFailure() })

Installation

Xcode

Follow the official guide to add to your Xcode project

1. Add the following package to the product target:

   https://github.com/vinceplusplus/TestableAssertSupport
   

2. Add the following package to the unit test target:

   https://github.com/vinceplusplus/TestableAssert
   

3. Add a configuration file to the product target to override built-in assertion functions:

   // TestableAssertSupport+Configuration.swift
   
   import TestableAssertSupport
   
   func assert(_ condition: @autoclosure () -> Bool, _ message: @autoclosure () -> String = String(), file: StaticString = #file, line: UInt = #line) {
     AssertFuncBodies.assert(condition(), message(), file, line)
   }
   
   func assertionFailure(_ message: @autoclosure () -> String = String(), file: StaticString = #file, line: UInt = #line) {
     AssertFuncBodies.assertionFailure(message(), file, line)
   }
   
   func precondition(_ condition: @autoclosure () -> Bool, _ message: @autoclosure () -> String = String(), file: StaticString = #file, line: UInt = #line) {
     AssertFuncBodies.precondition(condition(), message(), file, line)
   }
   
   func preconditionFailure(_ message: @autoclosure () -> String = String(), file: StaticString = #file, line: UInt = #line) -> Never {
     AssertFuncBodies.preconditionFailure(message(), file, line)
   }
   
   func fatalError(_ message: @autoclosure () -> String = String(), file: StaticString = #file, line: UInt = #line) -> Never {
     AssertFuncBodies.fatalError(message(), file, line)
   }
   

Swift Package Manager

1. Add the following package dependencies:

   .package(url: "https://github.com/vinceplusplus/TestableAssertSupport", from: "1.0.0"),
   .package(url: "https://github.com/vinceplusplus/TestableAssert", from: "1.0.0"),
   

2. Add TestableAssertSupport as a dependency to the product target
3. Add TestableAssert as a dependency to the test target
4. Add a configuration file to the product target to override built-in assertion functions:

   // TestableAssertSupport+Configuration.swift
   
   import TestableAssertSupport
   
   func assert(_ condition: @autoclosure () -> Bool, _ message: @autoclosure () -> String = String(), file: StaticString = #file, line: UInt = #line) {
     AssertFuncBodies.assert(condition(), message(), file, line)
   }
   
   func assertionFailure(_ message: @autoclosure () -> String = String(), file: StaticString = #file, line: UInt = #line) {
     AssertFuncBodies.assertionFailure(message(), file, line)
   }
   
   func precondition(_ condition: @autoclosure () -> Bool, _ message: @autoclosure () -> String = String(), file: StaticString = #file, line: UInt = #line) {
     AssertFuncBodies.precondition(condition(), message(), file, line)
   }
   
   func preconditionFailure(_ message: @autoclosure () -> String = String(), file: StaticString = #file, line: UInt = #line) -> Never {
     AssertFuncBodies.preconditionFailure(message(), file, line)
   }
   
   func fatalError(_ message: @autoclosure () -> String = String(), file: StaticString = #file, line: UInt = #line) -> Never {
     AssertFuncBodies.fatalError(message(), file, line)
   }