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Improve XCTAssertUnorderedEqualSequences complexity to O(n) for Hashable elements #285

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Improve XCTAssertUnorderedEqualSequences complexity to O(n) for Hashable elements #285

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38 changes: 37 additions & 1 deletion Tests/SwiftAlgorithmsTests/TestUtilities.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -85,7 +85,43 @@ func expectEqualSequences<S1: Sequence, S2: Sequence>(
message(), file: file, line: line)
}

// Two sequences contains exactly the same element but not necessarily in the same order.
// Two sequences contain exactly the same elements but not necessarily in the same order.
func expectUnorderedEqualSequences<S1: Sequence, S2: Sequence>(
_ expression1: @autoclosure () throws -> S1,
_ expression2: @autoclosure () throws -> S2,
file: StaticString = (#file), line: UInt = #line
) rethrows where S1.Element: Hashable, S1.Element == S2.Element {
var counts: [S1.Element: Int] = [:]
for elt in try expression1() {
counts[elt, default: 0] += 1
}
var missing: [S1.Element] = []
for elt in try expression2() {
if let count = counts[elt], count > 0 {
if count == 1 {
counts.removeValue(forKey: elt)
} else {
counts[elt] = count - 1
}
} else {
missing.append(elt)
}
}

XCTAssertTrue(
missing.isEmpty,
"first sequence missing '\(missing)' elements from second sequence",
file: file, line: line
)

let remaining = counts.flatMap { elt, count in repeatElement(elt, count: count) }
XCTAssertTrue(
counts.isEmpty, "first sequence contains \(remaining) missing from second sequence",
file: file, line: line
)
}

// Two sequences contain exactly the same elements but not necessarily in the same order (fallback for non-Hashable Equatable elements).
func expectUnorderedEqualSequences<S1: Sequence, S2: Sequence>(
_ expression1: @autoclosure () throws -> S1,
_ expression2: @autoclosure () throws -> S2,
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