Add DealerTests test target

Author: mattt

Package.swift

@@ -28,5 +28,8 @@ let package = Package(
         .target(
             name: "Dealer",
             dependencies: ["DeckOfPlayingCards"]),
+        .testTarget(
+            name: "DealerTests",
+            dependencies: ["Dealer"]),
     ]
 )

Tests/DealerTests/DealerTests.swift

@@ -0,0 +1,57 @@
+/*
+ This source file is part of the Swift.org open source project
+
+ Copyright 2021 Apple Inc. and the Swift project authors
+ Licensed under Apache License v2.0 with Runtime Library Exception
+
+ See http://swift.org/LICENSE.txt for license information
+ See http://swift.org/CONTRIBUTORS.txt for Swift project authors
+*/
+
+import XCTest
+import class Foundation.Bundle
+
+final class DealerTests: XCTestCase {
+    func testExample() throws {
+        // This is an example of a functional test case.
+        // Use XCTAssert and related functions to verify your tests produce the correct
+        // results.
+
+        // Some of the APIs that we use below are available in macOS 10.13 and above.
+        guard #available(macOS 10.13, *) else {
+            return
+        }
+
+        // Mac Catalyst won't have `Process`, but it is supported for executables.
+        #if !targetEnvironment(macCatalyst)
+
+        let dealerBinary = productsDirectory.appendingPathComponent("Dealer")
+
+        let process = Process()
+        process.executableURL = dealerBinary
+
+        let pipe = Pipe()
+        process.standardOutput = pipe
+
+        try process.run()
+        process.waitUntilExit()
+
+        let data = pipe.fileHandleForReading.readDataToEndOfFile()
+        let output = String(data: data, encoding: .utf8)
+
+        XCTAssertNotEqual(output, "")
+        #endif
+    }
+
+    /// Returns path to the built products directory.
+    var productsDirectory: URL {
+      #if os(macOS)
+        for bundle in Bundle.allBundles where bundle.bundlePath.hasSuffix(".xctest") {
+            return bundle.bundleURL.deletingLastPathComponent()
+        }
+        fatalError("couldn't find the products directory")
+      #else
+        return Bundle.main.bundleURL
+      #endif
+    }
+}