Adopt resource bundles for the SPM test target.

Gzip.xcodeproj/project.pbxproj

@@ -225,7 +225,6 @@
 			isa = PBXGroup;
 			children = (
 				2A7DC79E1FB6AFC900539D90 /* GzipTests */,
-				2A8219C61D65AFB300D65063 /* test.txt.gz */,
 			);
 			path = Tests;
 			sourceTree = "<group>";
@@ -234,6 +233,7 @@
 			isa = PBXGroup;
 			children = (
 				2A58A75C1B00F414005FBBC2 /* GzipTests.swift */,
+				2A8219C61D65AFB300D65063 /* test.txt.gz */,
 			);
 			path = GzipTests;
 			sourceTree = "<group>";

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.0
+// swift-tools-version:5.3
 
 import PackageDescription
 
@@ -10,7 +10,11 @@ let package = Package(
     targets: [
         .target(name: "Gzip", dependencies: ["system-zlib"]),
         .target(name: "system-zlib"),
-        .testTarget(name: "GzipTests", dependencies: ["Gzip"]),
+        .testTarget(
+          name: "GzipTests",
+          dependencies: ["Gzip"],
+          resources: [.copy("./test.txt.gz")]
+        ),
     ],
     swiftLanguageVersions: [
         .v5,

Tests/GzipTests/GzipTests.swift

@@ -127,10 +127,7 @@ private extension XCTestCase {
     func bundleFile(name: String) -> URL {
         
         #if SWIFT_PACKAGE
-            return URL(fileURLWithPath: #file)
-                .deletingLastPathComponent()
-                .deletingLastPathComponent()
-                .appendingPathComponent(name)
+            return Bundle.module.url(forResource: name, withExtension: nil)!
         #else
             return Bundle(for: type(of: self)).url(forResource: name, withExtension: nil)!
         #endif