[Slider] added some Accessibility tests

Summary:
added test for traits
removed uiSlider test

Reviewers: #material_components_ios_owners, iangordon

Reviewed By: #material_components_ios_owners, iangordon

Subscribers: featherless

Projects: #material_components_ios

Differential Revision: http://codereview.cc/D97

Author: randallli

components/Slider/Slider.xcodeproj/project.pbxproj

@@ -500,6 +500,7 @@
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks";
 				PRODUCT_BUNDLE_IDENTIFIER = com.google.MaterialComponents.Slider;
 				PRODUCT_NAME = "$(TARGET_NAME)";
+				PROVISIONING_PROFILE = "";
 			};
 			name = Debug;
 		};
@@ -512,6 +513,7 @@
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks";
 				PRODUCT_BUNDLE_IDENTIFIER = com.google.MaterialComponents.Slider;
 				PRODUCT_NAME = "$(TARGET_NAME)";
+				PROVISIONING_PROFILE = "";
 			};
 			name = Release;
 		};

components/Slider/SliderTests/SliderTests.m

@@ -294,6 +294,91 @@ - (void)testTrackColorNullRestable {
   XCTAssertEqualObjects(actualColor, expectedColor);
 }
 
+#pragma mark accessibility
+
+- (void)testAccessibilityValue {
+  // Given
+  MDCSlider *slider = [[MDCSlider alloc] init];
+  CGFloat newValue = [self randomPercent];
+
+  // When
+  slider.value = newValue;
+
+  // Then
+  NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc] init];
+  numberFormatter.numberStyle = NSNumberFormatterPercentStyle;
+  NSString *expected = [numberFormatter stringFromNumber:[NSNumber numberWithFloat:slider.value]];
+  XCTAssertEqualObjects([slider accessibilityValue], expected);
+}
+
+- (void)testAccessibilityValueWithLargerMax {
+  // Given
+  MDCSlider *slider = [[MDCSlider alloc] init];
+  slider.maximumValue = [self randomNumber];
+  CGFloat newValue = [self randomPercent];
+
+  // When
+  slider.value = newValue;
+
+  // Then
+  NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc] init];
+  numberFormatter.numberStyle = NSNumberFormatterPercentStyle;
+  CGFloat percent = (slider.value - slider.minimumValue) / (slider.maximumValue - slider.minimumValue);
+  NSString *expected = [numberFormatter stringFromNumber:[NSNumber numberWithFloat:percent]];
+  XCTAssertEqualObjects([slider accessibilityValue], expected);
+}
+
+- (void)testAccessibilityIncrement {
+  // Given
+  MDCSlider *slider = [[MDCSlider alloc] init];
+  slider.value = [self randomPercent] - 0.1f;
+  CGFloat originalValue = slider.value;
+
+  // When
+  [slider accessibilityIncrement];
+
+  // Then
+  XCTAssertEqual(originalValue + 0.1f, slider.value);
+}
+
+- (void)testAccessibilityDecrement {
+  // Given
+  MDCSlider *slider = [[MDCSlider alloc] init];
+  slider.value = [self randomPercent] + 0.1f;
+  CGFloat originalValue = slider.value;
+
+  // When
+  [slider accessibilityDecrement];
+
+  // Then
+  XCTAssertEqual(originalValue - 0.1f, slider.value);
+}
+
+- (void)testAccessibilityIncrementWithLargerMax {
+  // Given
+  MDCSlider *slider = [[MDCSlider alloc] init];
+  slider.maximumValue = [self randomNumber];
+  slider.value = ([self randomPercent] - 0.1f) * slider.maximumValue;
+  CGFloat originalValue = slider.value;
+
+  // When
+  [slider accessibilityIncrement];
+
+  // Then
+  XCTAssertEqual(originalValue + 0.1f * slider.maximumValue, slider.value);
+}
+
+- (void)testAccessibilityTraits {
+  // Given
+  MDCSlider *slider = [[MDCSlider alloc] init];
+  slider.enabled = arc4random_uniform(2);  // It does not matter if the slider is enabled or disabled.
+
+  // When
+
+  // Then
+  XCTAssertTrue(slider.accessibilityTraits & UIAccessibilityTraitAdjustable);
+}
+
 #pragma mark private test helpers
 
 - (UIColor *)blueColor {
@@ -305,7 +390,7 @@ - (CGFloat)randomNumber {
 }
 
 - (CGFloat)randomPercent {
-  return 1 / (CGFloat)(arc4random_uniform(999) + 1);
+  return (CGFloat)(arc4random_uniform(1001)) / 1000;
 }
 
 @end

components/Slider/src/MDCSlider.m

@@ -23,7 +23,7 @@
 static const CGFloat kSliderMinTouchSize = 48.0f;
 static const CGFloat kSliderThumbRadius = 6.0f;
 static const CGFloat kSliderThumbMaxRippleRadius = 16.0f;
-static const CGFloat kSliderAccessibilityIncrement = 0.1f;  // Matches UISlider's increment.
+static const CGFloat kSliderAccessibilityIncrement = 0.1f;  // Matches UISlider's percent increment.
 static const CGFloat kSliderLightThemeTrackAlpha = 0.26f;
 
 @interface MDCSlider () <MDCThumbTrackDelegate>
@@ -67,7 +67,7 @@ - (instancetype)initWithFrame:(CGRect)frame {
 
 #pragma mark - ThumbTrack passthrough methods
 
--(void)setTrackBackgroundColor:(UIColor *)trackBackgroundColor {
+- (void)setTrackBackgroundColor:(UIColor *)trackBackgroundColor {
   _thumbTrack.trackOffColor = trackBackgroundColor ?: [[self class] defaultTrackOffColor];
   ;
 }
@@ -165,10 +165,19 @@ - (BOOL)isAccessibilityElement {
 }
 
 - (NSString *)accessibilityValue {
-  return [NSString stringWithFormat:@"%0.1f", self.value];
+  static dispatch_once_t onceToken;
+  static NSNumberFormatter *numberFormatter;
+  dispatch_once(&onceToken, ^{
+    numberFormatter = [[NSNumberFormatter alloc] init];
+    numberFormatter.numberStyle = NSNumberFormatterPercentStyle;
+  });
+  CGFloat percentage = (self.value - self.minimumValue) / (self.maximumValue - self.minimumValue);
+  return [numberFormatter stringFromNumber:@(percentage)];
 }
 
 - (UIAccessibilityTraits)accessibilityTraits {
+  // Adding UIAccessibilityTraitAdjustable also causes an iOS accessibility hint to be spoken:
+  // "Swipe up or down with one finger to adjust the value."
   UIAccessibilityTraits traits = super.accessibilityTraits | UIAccessibilityTraitAdjustable;
   if (!self.enabled) {
     traits |= UIAccessibilityTraitNotEnabled;