Ensure DecayAnimation Completion Block is Called Only Once. Fixes #1

Sources/Motion/Animations/BasicAnimation.swift

@@ -129,8 +129,8 @@ public final class BasicAnimation<Value: SIMDRepresentable>: ValueAnimation<Valu
      Stops the animation and optionally resolves it immediately (jumping to the `toValue`).
 
      - Parameters:
-        - resolveImmediately: Whether or not the animation should jump to the `toValue` without animation. Defaults to `false`.
-        - postValueChanged: If `true` is supplied for `resolveImmediately`, this controls whether not `valueChanged` upon changing `value` to toValue`.
+        - resolveImmediately: Whether or not the animation should jump to the `toValue` without animation and invoke the completion. Defaults to `false`.
+        - postValueChanged: If `true` is supplied for `resolveImmediately`, this controls whether not `valueChanged` is called upon changing `value` to `toValue`.
      */
     public override func stop(resolveImmediately: Bool = false, postValueChanged: Bool = false) {
         super.stop(resolveImmediately: resolveImmediately, postValueChanged: postValueChanged)

Sources/Motion/Animations/DecayAnimation.swift

@@ -82,16 +82,20 @@ public final class DecayAnimation<Value: SIMDRepresentable>: ValueAnimation<Valu
      Stops the animation and optionally resolves it immediately.
 
      - Parameters:
-        - resolveImmediately: Whether or not the animation should jump to its projected value without animation. Defaults to `false`.
-        - postValueChanged: If `true` is supplied for `resolveImmediately`, this controls whether not `valueChanged` upon changing `value` to the end value.
+        - resolveImmediately: Whether or not the animation should jump to zero `velocity` and invoke the completion. Defaults to `false`.
+        - postValueChanged: If `true` is supplied for `resolveImmediately`, this controls whether not `valueChanged` is called upon changing `value` to the end value.
 
      - Note: `resolveImmediately` and `postValueChanged` currently are ignored.
      They will be implemented at a later date when the logic for projecting decaying functions is worked out.
      */
     public override func stop(resolveImmediately: Bool = false, postValueChanged: Bool = false) {
         // We don't call super here, as jumping to the end requires knowing the end point, and we don't know that (yet).
         self.enabled = false
-        completion?()
+        self.velocity = .zero
+
+        if resolveImmediately {
+            completion?()
+        }
     }
 
     // MARK: - Disabled API

Sources/Motion/Animations/SpringAnimation.swift

@@ -246,8 +246,8 @@ public final class SpringAnimation<Value: SIMDRepresentable>: ValueAnimation<Val
      Stops the animation and optionally resolves it immediately (jumping to the `toValue`).
 
      - Parameters:
-        - resolveImmediately: Whether or not the animation should jump to the `toValue` without animation. Defaults to `false`.
-        - postValueChanged: If `true` is supplied for `resolveImmediately`, this controls whether not `valueChanged` upon changing `value` to toValue`.
+        - resolveImmediately: Whether or not the animation should jump to the `toValue` without animation and invoke the completion. Defaults to `false`.
+        - postValueChanged: If `true` is supplied for `resolveImmediately`, this controls whether not `valueChanged` is called upon changing `value` to `toValue`.
      */
     public override func stop(resolveImmediately: Bool = false, postValueChanged: Bool = false) {
         super.stop(resolveImmediately: resolveImmediately, postValueChanged: postValueChanged)

Tests/MotionTests/BasicAnimationTests.swift

@@ -76,7 +76,8 @@ final class BasicAnimationTests: XCTestCase {
             expectCompletionCalled.fulfill()
         }
 
-        tickAnimationUntilResolved(basicAnimation)
+        tickAnimationForDuration(basicAnimation, maxDuration: 0.1)
+        basicAnimation.stop(resolveImmediately: true, postValueChanged: true)
 
         wait(for: [expectValueChangedCalled, expectCompletionCalled], timeout: 0.0)
     }

Tests/MotionTests/DecayAnimationTests.swift

@@ -58,6 +58,26 @@ final class DecayAnimationTests: XCTestCase {
         wait(for: [expectCompletionCalled, expectDecayVelocityZero], timeout: 0.0)
     }
 
+    func testDecayResolveImmediately() {
+        let decay = DecayAnimation<CGFloat>()
+
+        let expectCompletionCalled = XCTestExpectation(description: "Decay animated from \(decay.value) to ")
+        let expectDecayVelocityZero = XCTestExpectation(description: "Decay animated from \(decay.value) to ")
+        decay.completion = { [unowned decay] in
+            expectCompletionCalled.fulfill()
+
+            if decay.velocity <= 0.5 {
+                expectDecayVelocityZero.fulfill()
+            }
+        }
+        decay.velocity = 2000.0
+
+        tickAnimationForDuration(decay, maxDuration: 0.1)
+        decay.stop(resolveImmediately: true, postValueChanged: true)
+
+        wait(for: [expectCompletionCalled, expectDecayVelocityZero], timeout: 0.0)
+    }
+
     // MARK: - CAKeyframeAnimationEmittable Tests
 
     func testCreateCAKeyframeAnimationFromDecayAnimation() {

Tests/MotionTests/SpringAnimationTests.swift

@@ -149,7 +149,8 @@ final class SpringAnimationTests: XCTestCase {
             expectCompletionCalled.fulfill()
         }
 
-        tickAnimationUntilResolved(spring)
+        tickAnimationForDuration(spring, maxDuration: 0.1)
+        spring.stop(resolveImmediately: true, postValueChanged: true)
 
         wait(for: [expectValueChangedCalled, expectCompletionCalled], timeout: 0.0)
     }