Add missing coverage

Tests/LayoutTests/LayoutItemTests.swift

@@ -714,6 +714,27 @@ final class LayoutItemTests: XCTestCase {
 
     // MARK: - Margins
 
+    func testToMargins_throwsAssertion() {
+
+        // GIVEN
+
+        let superview: UIView = .init()
+        let view: UIView = .init()
+        let item: LayoutItem = view.toMargins()
+
+        // THEN
+
+        expect(item.superviewConstraints(view)).to(throwAssertion())
+
+        // WHEN
+
+        superview.addSubview(view)
+
+        // THEN
+
+        expect(item.superviewConstraints(view).count) == 4
+    }
+
     func testToMarginsInsetsPriorityDirectional() {
         assertLayout(devices: Device.portraitTestDevices + Device.modernLandscapeTestDevices) { view in
             view.layout {
@@ -845,6 +866,27 @@ final class LayoutItemTests: XCTestCase {
 
     // MARK: - Safe Area
 
+    func testToSafeArea_throwsAssertion() {
+
+        // GIVEN
+
+        let superview: UIView = .init()
+        let view: UIView = .init()
+        let item: LayoutItem = view.toSafeArea()
+
+        // THEN
+
+        expect(item.superviewConstraints(view)).to(throwAssertion())
+
+        // WHEN
+
+        superview.addSubview(view)
+
+        // THEN
+
+        expect(item.superviewConstraints(view).count) == 4
+    }
+
     func testToSafeAreaInsetsPriorityDirectional() {
         assertLayout(devices: Device.allTestDevices) { view in
             view.layout {

Tests/LayoutTests/LayoutTests.swift

@@ -663,6 +663,40 @@ final class LayoutTests: XCTestCase {
         }
     }
 
+    func testEqualAttributesWithViews_givenEmptyArray() {
+
+        // GIVEN
+
+        let superview: UIView = .init()
+        let view1: UIView = .init()
+        let view2: UIView = .init()
+        let layout: Layout = superview.layout().addItems(view1, view2)
+
+        // WHEN
+
+        layout.equal(.top, [])
+
+        // THEN
+
+        expect(layout.constraints).to(beEmpty())
+
+        // WHEN
+
+        layout.equal(.top, [view1])
+
+        // THEN
+
+        expect(layout.constraints).to(beEmpty())
+
+        // WHEN
+
+        layout.equal(.top, [view1, view2])
+
+        // THEN
+
+        expect(layout.constraints.count) == 1
+    }
+
     func testEqualSizeWithViews() {
 
         // GIVEN
@@ -721,6 +755,32 @@ final class LayoutTests: XCTestCase {
         }
     }
 
+    func testCenterViewBetweenLeadingAndTrailingPriority_givenNilSuperview() {
+
+        // GIVEN
+
+        var superview: UIView? = .init()
+        let view: UIView = .init()
+        let siblingView: UIView = .init()
+        let layout: Layout = superview!.layout().addItems(view, siblingView)
+        let leadingAnchor: NSLayoutXAxisAnchor = siblingView.trailing
+        let trailingAnchor: NSLayoutXAxisAnchor = superview!.trailing
+
+        // THEN
+
+        expect(layout.center(view, between: leadingAnchor, and: trailingAnchor)) === layout
+        expect(layout.constraints.count) == 3
+
+        // WHEN
+
+        superview = nil
+
+        // THEN
+
+        expect(layout.center(view, between: leadingAnchor, and: trailingAnchor)) === layout
+        expect(layout.constraints.count) == 3
+    }
+
     func testCenterViewBetweenTopAndBottomPriority() {
 
         // GIVEN
@@ -755,6 +815,32 @@ final class LayoutTests: XCTestCase {
         }
     }
 
+    func testCenterViewBetweenTopAndBottomPriority_givenNilSuperview() {
+
+        // GIVEN
+
+        var superview: UIView? = .init()
+        let view: UIView = .init()
+        let siblingView: UIView = .init()
+        let layout: Layout = superview!.layout().addItems(view, siblingView)
+        let topAnchor: NSLayoutYAxisAnchor = siblingView.bottom
+        let bottomAnchor: NSLayoutYAxisAnchor = superview!.bottom
+
+        // THEN
+
+        expect(layout.center(view, between: topAnchor, and: bottomAnchor)) === layout
+        expect(layout.constraints.count) == 3
+
+        // WHEN
+
+        superview = nil
+
+        // THEN
+
+        expect(layout.center(view, between: topAnchor, and: bottomAnchor)) === layout
+        expect(layout.constraints.count) == 3
+    }
+
     // MARK: - Stack
 
     func testHorizontalViewsSpacingDirectionPriorityAlignment() {
@@ -848,6 +934,40 @@ final class LayoutTests: XCTestCase {
         }
     }
 
+    func testHorizontalViewsSpacingDirectionPriorityAlignment_givenEmptyArray() {
+
+        // GIVEN
+
+        let superview: UIView = .init()
+        let view1: UIView = .init()
+        let view2: UIView = .init()
+        let layout: Layout = superview.layout().addItems(view1, view2)
+
+        // WHEN
+
+        layout.horizontal([])
+
+        // THEN
+
+        expect(layout.constraints).to(beEmpty())
+
+        // WHEN
+
+        layout.horizontal([view1])
+
+        // THEN
+
+        expect(layout.constraints).to(beEmpty())
+
+        // WHEN
+
+        layout.horizontal([view1, view2])
+
+        // THEN
+
+        expect(layout.constraints.count) == 1
+    }
+
     func testVerticalViewsSpacingPriorityAlignment() {
 
         // GIVEN
@@ -916,6 +1036,40 @@ final class LayoutTests: XCTestCase {
         }
     }
 
+    func testVerticalViewsSpacingPriorityAlignment_givenEmptyArray() {
+
+        // GIVEN
+
+        let superview: UIView = .init()
+        let view1: UIView = .init()
+        let view2: UIView = .init()
+        let layout: Layout = superview.layout().addItems(view1, view2)
+
+        // WHEN
+
+        layout.vertical([])
+
+        // THEN
+
+        expect(layout.constraints).to(beEmpty())
+
+        // WHEN
+
+        layout.vertical([view1])
+
+        // THEN
+
+        expect(layout.constraints).to(beEmpty())
+
+        // WHEN
+
+        layout.vertical([view1, view2])
+
+        // THEN
+
+        expect(layout.constraints.count) == 1
+    }
+
     // MARK: - Visual Format Language
 
     func testHorizontalWithFormatMetricsOptions_givenDefaults() {

Tests/LayoutTests/UIKit/NSDirectionalEdgeInsetsTests.swift

@@ -13,6 +13,10 @@ import XCTest
 
 final class NSDirectionalEdgeInsetsTests: XCTestCase {
 
+    func testEdgeType() {
+        expect(NSDirectionalEdgeInsets().edgeType == DirectionalEdge.self) == true
+    }
+
     func testInitWithInset() {
 
         // GIVEN

Tests/LayoutTests/UIKit/UIEdgeInsetsTests.swift

@@ -14,6 +14,10 @@ import XCTest
 
 final class UIEdgeInsetsTests: XCTestCase {
 
+    func testEdgeType() {
+        expect(UIEdgeInsets().edgeType == CanonicalEdge.self) == true
+    }
+
     func testInitWithInset() {
 
         // GIVEN

Tests/LayoutTests/UIKit/UIView+AutoLayoutTests.swift

@@ -458,6 +458,26 @@ final class UIViewAutoLayoutTests: XCTestCase {
         expect(constraints2.first?.constant) == 5
     }
 
+    func testConstraintForAttributeIsRelationToSuperviewMultiplierConstant_givenNilSuperview() {
+
+        // GIVEN
+
+        let superview: UIView = .init()
+        let view: UIView = .init()
+
+        // THEN
+
+        expect(view.constraints(toSuperview: [.top])).to(throwAssertion())
+
+        // WHEN
+
+        superview.addSubview(view)
+
+        // THEN
+
+        expect(view.constraints(toSuperview: [.top]).count) == 1
+    }
+
     func testConstraintForAttributeIsRelationToTargetAttributeOfTargetViewMultiplierConstant() {
 
         // GIVEN