Add testComputeTreeHash

Tests/SotoCoreTests/MiddlewareTests.swift

@@ -141,4 +141,38 @@ class MiddlewareTests: XCTestCase {
             XCTAssertEqual(request.url.absoluteString, "https://bucket.s3-accelerate.dualstack.amazonaws.com/file")
         }
     }
+
+    // create a buffer of random values. Will always create the same given you supply the same z and w values
+    // Random number generator from https://www.codeproject.com/Articles/25172/Simple-Random-Number-Generation
+    func createRandomBuffer(_ w: UInt, _ z: UInt, size: Int) -> [UInt8] {
+        var z = z
+        var w = w
+        func getUInt8() -> UInt8 {
+            z = 36969 * (z & 65535) + (z >> 16)
+            w = 18000 * (w & 65535) + (w >> 16)
+            return UInt8(((z << 16) + w) & 0xFF)
+        }
+        var data = [UInt8](repeating: 0, count: size)
+        for i in 0..<size {
+            data[i] = getUInt8()
+        }
+        return data
+    }
+
+    func testComputeTreeHash() throws {
+        //  create buffer full of random data, use the same seeds to ensure we get the same buffer everytime
+        let data = self.createRandomBuffer(23, 4, size: 7 * 1024 * 1024 + 258)
+
+        // create byte buffer
+        var byteBuffer = ByteBufferAllocator().buffer(capacity: data.count)
+        byteBuffer.writeBytes(data)
+
+        let middleware = TreeHashMiddleware(header: "tree-hash")
+        let treeHash = try middleware.computeTreeHash(byteBuffer)
+
+        XCTAssertEqual(
+            treeHash,
+            [210, 50, 5, 126, 16, 6, 59, 6, 21, 40, 186, 74, 192, 56, 39, 85, 210, 25, 238, 54, 4, 252, 221, 238, 107, 127, 76, 118, 245, 76, 22, 45]
+        )
+    }
 }