TestCases.swift

import CustomDump
import Testing

// Swift Testing-ified spiritual successor to https://github.com/ZevEisenberg/TestCleaner

/// A container for a list of test cases.
///
/// Use this when Swift Testing’s [parameterized tests](https://developer.apple.com/documentation/testing/parameterizedtesting) are not appropriate, such as when the construction of the test cases requires interacting with our internal dependency injection container, which requires state to be set via a test suite trait.
public struct TestCases<each Value> {
  var testCases: [TestCase<repeat each Value>]

  public init(
    _ testCases: [TestCase<repeat each Value>]
  ) {
    self.testCases = testCases
  }
}

/// A single test case. Carries source location information so test failures can pinpoint the relevant test case in the source editor (if not the test navigator).
public struct TestCase<each Value> {
  var value: (repeat each Value)
  var involvement: TestInvolvement?
  var sourceLocation: SourceLocation
  var customDumpSourceLocation: CustomDumpSourceLocation

  public init(
    _ value: repeat each Value,
    involvement: TestInvolvement? = nil,
    sourceLocation: SourceLocation = #_sourceLocation,
    fileID: StaticString = #fileID,
    filePath: StaticString = #filePath,
    line: UInt = #line,
    column: UInt = #column
  ) {
    self.value = (repeat each value)
    self.involvement = involvement
    self.sourceLocation = sourceLocation
    self.customDumpSourceLocation = CustomDumpSourceLocation(
      fileID: fileID,
      filePath: filePath,
      line: line,
      column: column
    )
  }
}

/// Whether a test case is excluded or focused in a test run.
public enum TestInvolvement {
  /// This test case is excluded, and will not be evaluated when the test is run
  case excluded

  /// This test case is focused, meaning that only it and other focused test cases will be evaluated. All non-focused test cases will be excluded.
  case focused
}

/// Creates a test case that is skipped when running the enclosing test.
public func xTestCase<each Value>(
  _ value: repeat (each Value),
  involvement: TestInvolvement? = nil,
  sourceLocation: SourceLocation = #_sourceLocation,
  fileID: StaticString = #fileID,
  filePath: StaticString = #filePath,
  line: UInt = #line,
  column: UInt = #column
) -> TestCase<repeat each Value> {
  TestCase(
    repeat each value,
    involvement: .excluded,
    sourceLocation: sourceLocation,
    fileID: fileID,
    filePath: filePath,
    line: line,
    column: column
  )
}

/// Creates a test case that is always run when the enclosing test is run. Causes any non-focused test cases to be skipped. If a test contains multiple focused test cases, they will all be run.
public func fTestCase<each Value>(
  _ value: repeat (each Value),
  involvement: TestInvolvement? = nil,
  sourceLocation: SourceLocation = #_sourceLocation,
  fileID: StaticString = #fileID,
  filePath: StaticString = #filePath,
  line: UInt = #line,
  column: UInt = #column
) -> TestCase<repeat each Value> {
  TestCase(
    repeat each value,
    involvement: .focused,
    sourceLocation: sourceLocation,
    fileID: fileID,
    filePath: filePath,
    line: line,
    column: column
  )
}

extension TestCases: Sequence {
  public typealias Element = (repeat each Value, SourceLocation, CustomDumpSourceLocation)

  public func makeIterator() -> Iterator {
    Iterator(testCases: testCases.filteredForTesting())
  }

  public struct Iterator: IteratorProtocol {
    let testCases: [TestCase<repeat each Value>]
    var currentIndex = 0
    public mutating func next() -> Element? {
      defer {
        currentIndex += 1
      }
      guard testCases.indices.contains(currentIndex) else {
        return nil
      }
      let testCase = testCases[currentIndex]
      return (repeat each testCase.value, testCase.sourceLocation, testCase.customDumpSourceLocation)
    }
  }
}

extension Array {
  func filteredForTesting<each Value>() -> [TestCase<repeat each Value>]
    where Element == TestCase<repeat each Value>
  {
    if contains(where: { $0.involvement == .focused }) {
      return filter { $0.involvement == .focused }
    }
    return filter { $0.involvement != .excluded }
  }
}

public struct CustomDumpSourceLocation {
  let fileID: StaticString
  let filePath: StaticString
  let line: UInt
  let column: UInt

  public init(
    fileID: StaticString,
    filePath: StaticString,
    line: UInt,
    column: UInt
  ) {
    self.fileID = fileID
    self.filePath = filePath
    self.line = line
    self.column = column
  }
}

public func expectNoDifference<T: Equatable>(
  _ expression1: @autoclosure () throws -> T,
  _ expression2: @autoclosure () throws -> T,
  _ message: @autoclosure () -> String? = nil,
  sourceLocation: CustomDumpSourceLocation
) {
  expectNoDifference(
    try expression1(),
    try expression2(),
    message(),
    fileID: sourceLocation.fileID,
    filePath: sourceLocation.filePath,
    line: sourceLocation.line,
    column: sourceLocation.column
  )
}