Add test coverage for resource object compare(to:)

Tests/JSONAPITestingTests/Comparisons/ResourceObjectCompareTests.swift

@@ -12,32 +12,71 @@ import JSONAPITesting
 final class ResourceObjectCompareTests: XCTestCase {
     func test_same() {
         XCTAssertTrue(test1.compare(to: test1).differences.isEmpty)
-        XCTAssertTrue(test2.compare(to: test2).differences.isEmpty)
+        XCTAssertTrue(test1_differentId.compare(to: test1_differentId).differences.isEmpty)
+        XCTAssertTrue(test1_differentAttributes.compare(to: test1_differentAttributes).differences.isEmpty)
     }
 
     func test_differentAttributes() {
-        // TODO: write actual test
-        print(test1.compare(to: test2).differences.map { "\($0): \($1)" }.joined(separator: ", "))
+        XCTAssertEqual(test1.compare(to: test1_differentAttributes).differences, [
+            "'favoriteColor' attribute": #"Optional("red") ≠ nil"#,
+            "'name' attribute": "James ≠ Fred",
+            "'age' attribute": "12 ≠ 10"
+        ])
     }
 
     func test_differentRelationships() {
-        // TODO: write test
-    }
-
-    func test_differentTypes() {
-        // TODO: write test
+        XCTAssertEqual(test1.compare(to: test1_differentRelationships).differences, [
+            "'parents' relationship": "4, 5 ≠ 3",
+            "'bestFriend' relationship": "Optional(Id(3)) ≠ nil"
+        ])
     }
 
     func test_differentIds() {
-        // TODO: write test
+        XCTAssertEqual(test1.compare(to: test1_differentId).differences, [
+            "id": "2 ≠ 3"
+        ])
     }
 
     func test_differentMetadata() {
-        // TODO: write test
+        let test1 = TestType2(
+            id: "2",
+            attributes: .none,
+            relationships: .none,
+            meta: .init(total: 10),
+            links: .init(link: .init(url: "http://google.com"))
+        )
+        let test1_differentMeta = TestType2(
+            id: "2",
+            attributes: .none,
+            relationships: .none,
+            meta: .init(total: 12),
+            links: .init(link: .init(url: "http://google.com"))
+        )
+
+        XCTAssertEqual(test1.compare(to: test1_differentMeta).differences, [
+            "meta": "total: 10 ≠ total: 12"
+        ])
     }
 
     func test_differentLinks() {
-        // TODO: write test
+        let test1 = TestType2(
+            id: "2",
+            attributes: .none,
+            relationships: .none,
+            meta: .init(total: 10),
+            links: .init(link: .init(url: "http://google.com"))
+        )
+        let test1_differentLinks = TestType2(
+            id: "2",
+            attributes: .none,
+            relationships: .none,
+            meta: .init(total: 10),
+            links: .init(link: .init(url: "http://yahoo.com"))
+        )
+
+        XCTAssertEqual(test1.compare(to: test1_differentLinks).differences, [
+            "links": "link: http://google.com ≠ link: http://yahoo.com"
+        ])
     }
 
     fileprivate let test1 = TestType(
@@ -54,15 +93,43 @@ final class ResourceObjectCompareTests: XCTestCase {
         links: .none
     )
 
-    fileprivate let test2 = TestType(
+    fileprivate let test1_differentId = TestType(
         id: "3",
+        attributes: .init(
+            name: "James",
+            age: 12,
+            favoriteColor: "red"),
+        relationships: .init(
+            bestFriend: "3",
+            parents: ["4", "5"]
+        ),
+        meta: .none,
+        links: .none
+    )
+
+    fileprivate let test1_differentAttributes = TestType(
+        id: "2",
         attributes: .init(
             name: "Fred",
             age: 10,
             favoriteColor: .init(value: nil)),
+        relationships: .init(
+            bestFriend: "3",
+            parents: ["4", "5"]
+        ),
+        meta: .none,
+        links: .none
+    )
+
+    fileprivate let test1_differentRelationships = TestType(
+        id: "2",
+        attributes: .init(
+            name: "James",
+            age: 12,
+            favoriteColor: "red"),
         relationships: .init(
             bestFriend: nil,
-            parents: ["1"]
+            parents: ["3"]
         ),
         meta: .none,
         links: .none
@@ -85,3 +152,29 @@ private enum TestDescription: JSONAPI.ResourceObjectDescription {
 }
 
 private typealias TestType = ResourceObject<TestDescription, NoMetadata, NoLinks, String>
+
+private struct TestMetadata: JSONAPI.Meta, CustomStringConvertible {
+    let total: Int
+
+    var description: String {
+        "total: \(total)"
+    }
+}
+
+private struct TestLinks: JSONAPI.Links, CustomStringConvertible {
+    let link: Link<String, NoMetadata>
+
+    var description: String {
+        "link: \(link.url)"
+    }
+}
+
+private enum TestDescription2: JSONAPI.ResourceObjectDescription {
+    static let jsonType: String = "test_type2"
+
+    typealias Attributes = NoAttributes
+
+    typealias Relationships = NoRelationships
+}
+
+private typealias TestType2 = ResourceObject<TestDescription2, TestMetadata, TestLinks, String>