fix: serialize schemes the way Xcode does

Fixtures/iOS/Project.xcodeproj/xcshareddata/xcschemes/iOS.xcscheme

@@ -81,12 +81,6 @@
             </ActionContent>
          </ExecutionAction>
       </PostActions>
-      <TestPlans>
-         <TestPlanReference
-            default = "YES"
-            reference = "container:iOS.xctestplan">
-         </TestPlanReference>
-      </TestPlans>
       <MacroExpansion>
          <BuildableReference
             BuildableIdentifier = "primary"
@@ -122,6 +116,12 @@
             isEnabled = "NO">
          </EnvironmentVariable>
       </EnvironmentVariables>
+      <TestPlans>
+         <TestPlanReference
+            reference = "container:iOS.xctestplan"
+            default = "YES">
+         </TestPlanReference>
+      </TestPlans>
    </TestAction>
    <LaunchAction
       buildConfiguration = "Debug"

Sources/XcodeProj/Extensions/AEXML+XcodeFormat.swift

@@ -86,6 +86,10 @@ let attributesOrder: [String: [String]] = [
         "value",
         "isEnabled",
     ],
+    "TestPlanReference": [
+        "reference",
+        "default",
+    ],
     "TestableReference": [
         "skipped",
         "parallelizable",

Sources/XcodeProj/Scheme/XCScheme+BuildAction.swift

@@ -158,8 +158,9 @@ public extension XCScheme {
                 attributes["buildArchitectures"] = buildArchitecturesXMLString
             }
 
-            if let runPostActionsOnFailure {
-                attributes["runPostActionsOnFailure"] = runPostActionsOnFailure.xmlString
+            // Xcode omits the attribute unless it is enabled.
+            if runPostActionsOnFailure == true {
+                attributes["runPostActionsOnFailure"] = true.xmlString
             }
 
             let element = AEXMLElement(name: "BuildAction",

Sources/XcodeProj/Scheme/XCScheme+LaunchAction.swift

@@ -445,7 +445,7 @@ public extension XCScheme {
                 macro.addChild(macroExpansion.xmlElement())
             }
 
-            if let commandlineArguments {
+            if let commandlineArguments, !commandlineArguments.arguments.isEmpty {
                 element.addChild(commandlineArguments.xmlElement())
             }
 

Sources/XcodeProj/Scheme/XCScheme+ProfileAction.swift

@@ -169,7 +169,7 @@ public extension XCScheme {
             if !enableTestabilityWhenProfilingTests {
                 element.attributes["enableTestabilityWhenProfilingTests"] = "No"
             }
-            if let commandlineArguments {
+            if let commandlineArguments, !commandlineArguments.arguments.isEmpty {
                 element.addChild(commandlineArguments.xmlElement())
             }
             if let environmentVariables {

Sources/XcodeProj/Scheme/XCScheme+TestAction.swift

@@ -204,24 +204,20 @@ public extension XCScheme {
             let element = AEXMLElement(name: "TestAction", value: nil, attributes: attributes)
             super.writeXML(parent: element)
 
-            if let testPlans {
-                let testPlansElement = element.addChild(name: "TestPlans")
-                for testPlan in testPlans {
-                    testPlansElement.addChild(testPlan.xmlElement())
-                }
-            }
-
             if let macroExpansion {
                 let macro = element.addChild(name: "MacroExpansion")
                 macro.addChild(macroExpansion.xmlElement())
             }
 
-            let testablesElement = element.addChild(name: "Testables")
-            for testable in testables {
-                testablesElement.addChild(testable.xmlElement())
+            // Xcode omits empty testables when the scheme uses test plans.
+            if !testables.isEmpty || testPlans == nil {
+                let testablesElement = element.addChild(name: "Testables")
+                for testable in testables {
+                    testablesElement.addChild(testable.xmlElement())
+                }
             }
 
-            if let commandlineArguments {
+            if let commandlineArguments, !commandlineArguments.arguments.isEmpty {
                 element.addChild(commandlineArguments.xmlElement())
             }
 
@@ -243,6 +239,13 @@ public extension XCScheme {
                 }
             }
 
+            if let testPlans {
+                let testPlansElement = element.addChild(name: "TestPlans")
+                for testPlan in testPlans {
+                    testPlansElement.addChild(testPlan.xmlElement())
+                }
+            }
+
             return element
         }
 

Tests/XcodeProjTests/Scheme/XCSchemeTests.swift

@@ -299,6 +299,37 @@ final class XCSchemeIntegrationTests: XCTestCase {
         XCTAssertEqual(subject, reconstructedSubject)
     }
 
+    func test_testAction_withTestPlans_serializesLikeXcode() throws {
+        // Given
+        let subject = try XCScheme.TestAction(buildConfiguration: "Debug",
+                                              macroExpansion: nil,
+                                              testPlans: [.init(reference: "container:App.xctestplan", default: true)],
+                                              codeCoverageTargets: [buildableReferenceWithStringBluePrint()],
+                                              commandlineArguments: .init(arguments: []))
+
+        // When
+        let element = subject.xmlElement()
+
+        // Then
+        XCTAssertEqual(element.children.map(\.name), ["CodeCoverageTargets", "TestPlans"])
+    }
+
+    func test_testAction_withoutTestPlans_keepsEmptyTestables() {
+        // Given
+        let subject = XCScheme.TestAction(buildConfiguration: "Debug", macroExpansion: nil)
+
+        // When
+        let element = subject.xmlElement()
+
+        // Then
+        XCTAssertEqual(element.children.map(\.name), ["Testables"])
+    }
+
+    func test_buildAction_runPostActionsOnFailure_onlySerializedWhenEnabled() {
+        XCTAssertNil(XCScheme.BuildAction(runPostActionsOnFailure: false).xmlElement().attributes["runPostActionsOnFailure"])
+        XCTAssertEqual(XCScheme.BuildAction(runPostActionsOnFailure: true).xmlElement().attributes["runPostActionsOnFailure"], "YES")
+    }
+
     func test_scheme_remoteRunnable() throws {
         // Given / When
         let subject = try XCScheme(path: watchAppSchemePath)