✅ Test synchronous shell output

tests/unit/Testables/Shell/RealShellTest.swift

@@ -23,6 +23,14 @@ class RealShellTest: XCTestCase {
         XCTAssertTrue(output.out.contains("Copyright (c) The PHP Group"))
     }
 
+    func test_system_shell_can_be_used_synchronously() {
+        XCTAssertTrue(Shell is RealShell)
+
+        let output = Shell.sync("php -v")
+
+        XCTAssertTrue(output.out.contains("Copyright (c) The PHP Group"))
+    }
+
     func test_system_shell_has_path() {
         let systemShell = Shell as! RealShell
 

tests/unit/Testables/Shell/TestableShellTest.swift

@@ -30,6 +30,35 @@ class TestableShellTest: XCTestCase {
 
         XCTAssertEqual("Hello world\nGoodbye world", output.out)
     }
+    
+    func test_fake_shell_synchronous_output() {
+        let greeting = BatchFakeShellOutput(items: [
+            .instant("Hello world\n"),
+            .delayed(0.2, "Goodbye world")
+        ])
+
+        let output = greeting.syncOutput()
+
+        XCTAssertEqual("Hello world\nGoodbye world", output.out)
+    }
+
+    func test_fake_shell_usage() {
+        let expectedOutput = """
+                PHP 8.3.0 (cli) (built: Nov 21 2023 14:40:35) (NTS)
+                Copyright (c) The PHP Group
+                Zend Engine v4.3.0, Copyright (c) Zend Technologies
+                with Xdebug v3.2.2, Copyright (c) 2002-2023, by Derick Rethans
+                with Zend OPcache v8.3.0, Copyright (c), by Zend Technologies
+                """
+
+        let shell = TestableShell(expectations: [
+            "php -v": .instant(expectedOutput),
+            "echo $PATH": .instant("/Users/user/bin:/opt/homebrew/bin")
+        ])
+
+        XCTAssertEqual(expectedOutput, shell.sync("php -v").out)
+        XCTAssertEqual("/Users/user/bin:/opt/homebrew/bin", shell.sync("echo $PATH").out)
+    }
 
     func test_fake_shell_has_path() {
         ActiveShell.useTestable([:])