Introduce ParsingTests (#235)

Introduce a unit test that parsers an entire build log. The build log represents a clean build of Backyard Birds on Xcode 15.1.

Author: cpisciotta

Package.swift

@@ -38,7 +38,10 @@ let package = Package(
         ),
         .testTarget(
             name: "XcbeautifyLibTests",
-            dependencies: ["XcbeautifyLib"]
+            dependencies: ["XcbeautifyLib"],
+            resources: [
+                .copy("ParsingTests/clean_build_xcode_15_1.txt"),
+            ]
         ),
     ]
 )

Tests/XcbeautifyLibTests/ParsingTests/ParsingTests.swift

@@ -0,0 +1,41 @@
+import XCTest
+@testable import XcbeautifyLib
+
+final class ParsingTests: XCTestCase {
+    func testCleanBuildXcode15_1() throws {
+        let url = Bundle.module.url(forResource: "clean_build_xcode_15_1", withExtension: "txt")!
+
+        var buildLog: [String] = try String(contentsOf: url)
+            .components(separatedBy: .newlines)
+
+        let parser = Parser(
+            colored: false,
+            renderer: .terminal,
+            preserveUnbeautifiedLines: false,
+            additionalLines: {
+                guard !buildLog.isEmpty else {
+                    XCTFail("The build log should never be empty when fetching additional lines.")
+                    return nil
+                }
+                return buildLog.removeFirst()
+            }
+        )
+
+        var uncapturedOutput = 0
+
+        while !buildLog.isEmpty {
+            let line = buildLog.removeFirst()
+            if !line.isEmpty, parser.parse(line: line) == nil {
+                uncapturedOutput += 1
+            }
+        }
+
+        // The following is a magic number.
+        // It represents the number of lines that aren't captured by the Parser.
+        // Slowly, this value should decrease until it reaches 0.
+        // It uses `XCTAssertEqual` instead of `XCTAssertLessThanOrEqual` as a reminder.
+        // Update this magic number whenever `uncapturedOutput` is less than the current magic number.
+        // There's a regression whenever `uncapturedOutput` is greater than the current magic number.
+        XCTAssertEqual(uncapturedOutput, 2218)
+    }
+}