If settlingDuration is unavailable, use the provided spring duration. (#5)

* If settlingDuration is unavailable, use the provided spring duration.

* Fix the tests.

Author: jverkoey

src/MDMMotionAnimator.m

@@ -184,7 +184,7 @@ - (void)addCoreAnimationTracer:(void (^)(CALayer *, CAAnimation *))tracer {
       if ([spring respondsToSelector:@selector(settlingDuration)]) {
         spring.duration = spring.settlingDuration;
       } else {
-        spring.duration = 1;
+        spring.duration = timing.duration;
       }
       animation = spring;
       break;

tests/unit/MotionAnimatorTests.m

@@ -146,7 +146,11 @@ - (void)testSpringAnimationFloatValue {
 
     XCTAssertEqual(springAnimation.keyPath, keyPath);
 
-    XCTAssertEqual(springAnimation.duration, springAnimation.settlingDuration);
+    if ([springAnimation respondsToSelector:@selector(settlingDuration)]) {
+      XCTAssertEqual(springAnimation.duration, springAnimation.settlingDuration);
+    } else {
+      XCTAssertEqual(springAnimation.duration, timing.duration);
+    }
     XCTAssertGreaterThan(springAnimation.beginTime, 0);
 
     XCTAssertTrue(springAnimation.additive);