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Fix inverted time factors in mixed glucose/time unit conversions #15

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Merged
ps2 merged 1 commit into from
Oct 26, 2026
Merged

Fix inverted time factors in mixed glucose/time unit conversions #15

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9 changes: 5 additions & 4 deletions Sources/LoopAlgorithm/LoopUnit.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -73,18 +73,19 @@ public enum LoopUnit: Sendable, CaseIterable {
(.milligramsPerDeciliterPerInternationalUnit, .millimolesPerLiterPerInternationalUnit):
return 1/UnitMolarMassBloodGlucoseDivisible
case (.milligramsPerDeciliterPerSecond, .millimolesPerLiterPerMinute):
return 1/UnitMolarMassBloodGlucoseDivisible / 60
case (.milligramsPerDeciliterPerMinute, .millimolesPerLiterPerSecond):
// Rate: per-second -> per-minute multiplies by 60 (opposite of a duration conversion)
return 1/UnitMolarMassBloodGlucoseDivisible * 60
case (.milligramsPerDeciliterPerMinute, .millimolesPerLiterPerSecond):
return 1/UnitMolarMassBloodGlucoseDivisible / 60
case (.millimolesPerLiter, .milligramsPerDeciliter),
(.millimolesPerLiterPerSecond, .milligramsPerDeciliterPerSecond),
(.millimolesPerLiterPerMinute, .milligramsPerDeciliterPerMinute),
(.millimolesPerLiterPerInternationalUnit, .milligramsPerDeciliterPerInternationalUnit):
return UnitMolarMassBloodGlucoseDivisible
case (.millimolesPerLiterPerSecond, .milligramsPerDeciliterPerMinute):
return UnitMolarMassBloodGlucoseDivisible / 60
case (.millimolesPerLiterPerMinute, .milligramsPerDeciliterPerSecond):
return UnitMolarMassBloodGlucoseDivisible * 60
case (.millimolesPerLiterPerMinute, .milligramsPerDeciliterPerSecond):
return UnitMolarMassBloodGlucoseDivisible / 60
case (.gram, _),
(.gramsPerUnit, _),
(.internationalUnit, _),
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35 changes: 31 additions & 4 deletions Tests/LoopAlgorithmTests/LoopUnitTests.swift
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Expand Up @@ -190,18 +190,45 @@ class LoopUnitTests: XCTestCase {

unit1 = LoopUnit.milligramsPerDeciliterPerMinute
unit2 = LoopUnit.millimolesPerLiterPerSecond
XCTAssertEqual(unit1.conversionFactor(toUnit: unit2), 1/UnitMolarMassBloodGlucoseDivisible * 60)
XCTAssertEqual(unit2.conversionFactor(toUnit: unit1), UnitMolarMassBloodGlucoseDivisible / 60)
XCTAssertEqual(unit1.conversionFactor(toUnit: unit2), 1/UnitMolarMassBloodGlucoseDivisible / 60)
XCTAssertEqual(unit2.conversionFactor(toUnit: unit1), UnitMolarMassBloodGlucoseDivisible * 60)

unit1 = LoopUnit.milligramsPerDeciliterPerSecond
unit2 = LoopUnit.millimolesPerLiterPerMinute
XCTAssertEqual(unit1.conversionFactor(toUnit: unit2), 1/UnitMolarMassBloodGlucoseDivisible / 60)
XCTAssertEqual(unit2.conversionFactor(toUnit: unit1), UnitMolarMassBloodGlucoseDivisible * 60)
XCTAssertEqual(unit1.conversionFactor(toUnit: unit2), 1/UnitMolarMassBloodGlucoseDivisible * 60)
XCTAssertEqual(unit2.conversionFactor(toUnit: unit1), UnitMolarMassBloodGlucoseDivisible / 60)

let quantity1 = LoopQuantity(unit: .millimolesPerLiter, doubleValue: 4)
let quantity2 = LoopQuantity(unit: .milligramsPerDeciliter, doubleValue: 72.06235200002165)
XCTAssertEqual(quantity1, quantity2)
}

/// The conversion table is maintained by hand, so check every pair against HealthKit,
/// which does the dimensional analysis for us. This guards against transcription errors
/// like the inverted time factor that made mg/dL·s -> mmol/L·min 3600x too small.
func testConversionFactorsMatchHealthKit() {
for source in LoopUnit.allCases {
for target in LoopUnit.allCases {
let context = "\(source.unitString) -> \(target.unitString)"
let one = HKQuantity(unit: HKUnit(from: source.unitString), doubleValue: 1)
let hkTarget = HKUnit(from: target.unitString)
let convertible = one.is(compatibleWith: hkTarget)

guard let factor = source.conversionFactor(toUnit: target) else {
XCTAssertFalse(convertible, "\(context) is convertible in HealthKit but returned nil")
continue
}

guard convertible else {
XCTFail("\(context) returned a factor but is not convertible in HealthKit")
continue
}

let expected = one.doubleValue(for: hkTarget)
XCTAssertEqual(factor, expected, accuracy: max(abs(expected) * 1e-12, .ulpOfOne), context)
}
}
}
}

extension LoopUnitTests {
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