diff --git a/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj b/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj
index 4d3770d04..714a08c44 100644
--- a/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj	
+++ b/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj	
@@ -972,6 +972,7 @@
 		4BC6236E26F4235400F83DFE /* Copper.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BC6236C26F4235400F83DFE /* Copper.cpp */; };
 		4BC6236F26F426B400F83DFE /* FAT.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B477709268FBE4D005C2340 /* FAT.cpp */; };
 		4BC6237226F94BCB00F83DFE /* MintermTests.mm in Sources */ = {isa = PBXBuildFile; fileRef = 4BC6237126F94BCB00F83DFE /* MintermTests.mm */; };
+		4BC62FF228A149300036AE59 /* NSData+dataWithContentsOfGZippedFile.m in Sources */ = {isa = PBXBuildFile; fileRef = 4BC62FF128A149300036AE59 /* NSData+dataWithContentsOfGZippedFile.m */; };
 		4BC751B21D157E61006C31D9 /* 6522Tests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4BC751B11D157E61006C31D9 /* 6522Tests.swift */; };
 		4BC76E691C98E31700E6EF73 /* FIRFilter.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BC76E671C98E31700E6EF73 /* FIRFilter.cpp */; };
 		4BC890D3230F86020025A55A /* DirectAccessDevice.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BC890D1230F86020025A55A /* DirectAccessDevice.cpp */; };
@@ -2056,6 +2057,8 @@
 		4BC6236C26F4235400F83DFE /* Copper.cpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.cpp; path = Copper.cpp; sourceTree = "<group>"; };
 		4BC6237026F94A5B00F83DFE /* Minterms.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = Minterms.hpp; sourceTree = "<group>"; };
 		4BC6237126F94BCB00F83DFE /* MintermTests.mm */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.objcpp; path = MintermTests.mm; sourceTree = "<group>"; };
+		4BC62FF028A149300036AE59 /* NSData+dataWithContentsOfGZippedFile.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = "NSData+dataWithContentsOfGZippedFile.h"; sourceTree = "<group>"; };
+		4BC62FF128A149300036AE59 /* NSData+dataWithContentsOfGZippedFile.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = "NSData+dataWithContentsOfGZippedFile.m"; sourceTree = "<group>"; };
 		4BC751B11D157E61006C31D9 /* 6522Tests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = 6522Tests.swift; sourceTree = "<group>"; };
 		4BC76E671C98E31700E6EF73 /* FIRFilter.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = FIRFilter.cpp; sourceTree = "<group>"; };
 		4BC76E681C98E31700E6EF73 /* FIRFilter.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = FIRFilter.hpp; sourceTree = "<group>"; };
@@ -4290,6 +4293,8 @@
 				4BFCA12A1ECBE7C400AC40C1 /* ZexallTests.swift */,
 				4B3BA0C41D318B44005DD7A7 /* Bridges */,
 				4B1414631B588A1100E04248 /* Test Binaries */,
+				4BC62FF028A149300036AE59 /* NSData+dataWithContentsOfGZippedFile.h */,
+				4BC62FF128A149300036AE59 /* NSData+dataWithContentsOfGZippedFile.m */,
 			);
 			path = "Clock SignalTests";
 			sourceTree = "<group>";
@@ -6132,6 +6137,7 @@
 				4B778F4F23A5F21C0000D260 /* StaticAnalyser.cpp in Sources */,
 				4B8DD3682633B2D400B3C866 /* SpectrumVideoContentionTests.mm in Sources */,
 				4B7752A928217E200073E2C5 /* 65816Storage.cpp in Sources */,
+				4BC62FF228A149300036AE59 /* NSData+dataWithContentsOfGZippedFile.m in Sources */,
 				4B7752AC28217E6E0073E2C5 /* StaticAnalyser.cpp in Sources */,
 				4B778F1223A5EC720000D260 /* CRT.cpp in Sources */,
 				4B778EF423A5DB3A0000D260 /* C1540.cpp in Sources */,
diff --git a/OSBindings/Mac/Clock SignalTests/AmigaBlitterTests.mm b/OSBindings/Mac/Clock SignalTests/AmigaBlitterTests.mm
index 5b9d71f46..64ad5e40c 100644
--- a/OSBindings/Mac/Clock SignalTests/AmigaBlitterTests.mm	
+++ b/OSBindings/Mac/Clock SignalTests/AmigaBlitterTests.mm	
@@ -9,10 +9,10 @@
 #import <XCTest/XCTest.h>
 
 #include "Blitter.hpp"
+#include "NSData+dataWithContentsOfGZippedFile.h"
 
 #include <unordered_map>
 #include <vector>
-#include <zlib.h>
 
 namespace Amiga {
 /// An empty stub to satisfy Amiga::Blitter's inheritance from Amiga::DMADevice;
@@ -38,32 +38,9 @@ struct Chipset {
 	Amiga::Chipset nonChipset;
 	Amiga::Blitter<true> blitter(nonChipset, ram, 256 * 1024);
 
-	NSURL *const traceURL = [[NSBundle bundleForClass:[self class]]
-		URLForResource:name withExtension:@"json.gz" subdirectory:@"Amiga Blitter Tests"];
-
-	// Use gzopen/etc to decompress to a temporary file, then read that back
-	// into memory to provide to the JSON deserialiser. This avoids having to wade
-	// too deeply into ZLib's slightly circuitous handling of decompression when
-	// the destination size is unkoinw.
-	NSString *const tempDir = NSTemporaryDirectory();
-	NSString *const tempFile = [tempDir stringByAppendingPathComponent:@"temp.json"];
-
-	const gzFile compressedFile = gzopen([traceURL fileSystemRepresentation], "rb");
-	FILE *const uncompressedFile = fopen([tempFile UTF8String], "wb");
-
-	uint8_t buffer[64 * 1024];
-	while(true) {
-		const auto length = gzread(compressedFile, buffer, sizeof(buffer));
-		if(!length) break;
-		fwrite(buffer, 1, length, uncompressedFile);
-		if(length != sizeof(buffer)) break;
-	}
-
-	fclose(uncompressedFile);
-	gzclose(compressedFile);
-
-	// Open and parse.
-	NSData *const traceData = [NSData dataWithContentsOfFile:tempFile];
+	NSString *const tracePath = [[NSBundle bundleForClass:[self class]]
+		pathForResource:name ofType:@"json.gz" inDirectory:@"Amiga Blitter Tests"];
+	NSData *const traceData = [NSData dataWithContentsOfGZippedFile:tracePath];
 	NSArray *const trace = [NSJSONSerialization JSONObjectWithData:traceData options:0 error:nil];
 	XCTAssertNotNil(trace);
 
diff --git a/OSBindings/Mac/Clock SignalTests/NSData+dataWithContentsOfGZippedFile.h b/OSBindings/Mac/Clock SignalTests/NSData+dataWithContentsOfGZippedFile.h
new file mode 100644
index 000000000..49ee06dde
--- /dev/null
+++ b/OSBindings/Mac/Clock SignalTests/NSData+dataWithContentsOfGZippedFile.h	
@@ -0,0 +1,19 @@
+//
+//  NSData+dataWithContentsOfGZippedFile.h
+//  Clock SignalTests
+//
+//  Created by Thomas Harte on 08/08/2022.
+//  Copyright © 2022 Thomas Harte. All rights reserved.
+//
+
+#import <Foundation/Foundation.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+@interface NSData (dataWithContentsOfGZippedFile)
+
++ (instancetype)dataWithContentsOfGZippedFile:(NSString *)path;
+
+@end
+
+NS_ASSUME_NONNULL_END
diff --git a/OSBindings/Mac/Clock SignalTests/NSData+dataWithContentsOfGZippedFile.m b/OSBindings/Mac/Clock SignalTests/NSData+dataWithContentsOfGZippedFile.m
new file mode 100644
index 000000000..2f3d7baa6
--- /dev/null
+++ b/OSBindings/Mac/Clock SignalTests/NSData+dataWithContentsOfGZippedFile.m	
@@ -0,0 +1,35 @@
+//
+//  NSData+dataWithContentsOfGZippedFile.m
+//  Clock SignalTests
+//
+//  Created by Thomas Harte on 08/08/2022.
+//  Copyright © 2022 Thomas Harte. All rights reserved.
+//
+
+#import "NSData+dataWithContentsOfGZippedFile.h"
+
+#include <zlib.h>
+
+@implementation NSData (dataWithContentsOfGZippedFile)
+
++ (instancetype)dataWithContentsOfGZippedFile:(NSString *)path {
+	gzFile compressedFile = gzopen([path UTF8String], "rb");
+	if(!compressedFile) {
+		return nil;
+	}
+
+	NSMutableData *data = [[NSMutableData alloc] init];
+
+	uint8_t buffer[64 * 1024];
+	while(true) {
+		int length = gzread(compressedFile, buffer, sizeof(buffer));
+		if(!length) break;
+		[data appendBytes:buffer length:length];
+		if(length != sizeof(buffer)) break;
+	}
+
+	gzclose(compressedFile);
+	return data;
+}
+
+@end