Refactor progress file parsing and improve test validation

Author: roulpriya

Sources/SwiftlyCore/FileManager+FilePath.swift

@@ -190,13 +190,6 @@ extension String {
         try self.write(to: URL(fileURLWithPath: path.string), atomically: atomically, encoding: enc)
     }
 
-    public func append(to path: FilePath, encoding enc: String.Encoding = .utf8) throws {
-        if !FileManager.default.fileExists(atPath: path.string) {
-            try self.write(to: path, atomically: true, encoding: enc)
-            return
-        }
-    }
-
     public init(contentsOf path: FilePath, encoding enc: String.Encoding = .utf8) throws {
         try self.init(contentsOf: URL(fileURLWithPath: path.string), encoding: enc)
     }

Tests/SwiftlyTests/InstallTests.swift

@@ -267,6 +267,7 @@ import Testing
     /// Verify that progress information is written to the progress file when specified.
     @Test(.testHomeMockedToolchain()) func installProgressFile() async throws {
         let progressFile = fs.mktemp(ext: ".json")
+        try await fs.create(.mode(0o644), file: progressFile)
 
         try await SwiftlyTests.runCommand(Install.self, [
             "install", "5.7.0",
@@ -276,20 +277,27 @@ import Testing
 
         #expect(try await fs.exists(atPath: progressFile))
 
+        let decoder = JSONDecoder()
         let progressContent = try String(contentsOfFile: progressFile.string)
-        let lines = progressContent.components(separatedBy: .newlines).filter { !$0.isEmpty }
+        let progressInfo = try progressContent.split(separator: "\n")
+            .filter { !$0.isEmpty }
+            .map { line in
+                try decoder.decode(ProgressInfo.self, from: Data(line.utf8))
+            }
 
-        #expect(!lines.isEmpty, "Progress file should contain progress entries")
+        #expect(!progressInfo.isEmpty, "Progress file should contain progress entries")
 
-        // Verify that at least one progress entry exists
-        let hasProgressEntry = lines.contains { line in
-            line.contains("\"step\"") && line.contains("\"percent\"") && line.contains("\"timestamp\"")
+        // Verify that at least one step progress entry exists
+        let hasStepEntry = progressInfo.contains { info in
+            if case .step = info { return true }
+            return false
         }
-        #expect(hasProgressEntry, "Progress file should contain step progress entries")
+        #expect(hasStepEntry, "Progress file should contain step progress entries")
 
         // Verify that a completion entry exists
-        let hasCompletionEntry = lines.contains { line in
-            line.contains("\"complete\"") && line.contains("\"success\"")
+        let hasCompletionEntry = progressInfo.contains { info in
+            if case .complete = info { return true }
+            return false
         }
         #expect(hasCompletionEntry, "Progress file should contain completion entry")