1 files changed, 49 insertions, 4 deletions
diff --git a/Tests/barTests/phbarTests.swift b/Tests/barTests/phbarTests.swift
index 6a2c4d5..982e728 100644
--- a/Tests/barTests/phbarTests.swift
+++ b/Tests/barTests/phbarTests.swift
@@ -1,8 +1,53 @@
+import Foundation
+import Synchronization
 import Testing
 @testable import bar
 
-@Test func example() async throws {
-    // Write your test here and use APIs like `#expect(...)` to check expected conditions.
-    // Swift Testing Documentation
-    // https://developer.apple.com/documentation/testing
+/// Blocking Runner work stays off the cooperative executor. The outer deadline
+/// also fails promptly if a regression prevents Runner from returning.
+private func runCommand(_ command: String, env: [String: String] = [:]) throws -> (lines: [String], diagnostics: Data) {
+    let url = FileManager.default.temporaryDirectory.appendingPathComponent(UUID().uuidString)
+    FileManager.default.createFile(atPath: url.path, contents: nil)
+    let output = try FileHandle(forWritingTo: url)
+    defer { try? FileManager.default.removeItem(at: url) }
+    let result = Mutex<[String]?>(nil)
+    let finished = DispatchSemaphore(value: 0)
+    DispatchQueue.global(qos: .utility).async {
+        let lines = Runner.run(command, env: env, errorOutput: output)
+        try? output.close()
+        result.withLock { $0 = lines }
+        finished.signal()
+    }
+    let completed = finished.wait(timeout: .now() + 5) == .success
+    try #require(completed, "Runner exceeded the five-second outer deadline")
+    return (try #require(result.withLock { $0 }), try Data(contentsOf: url))
+}
+
+@Test func drainsLargeStderrBeforeStdout() throws {
+    let result = try runCommand("/usr/bin/head -c 1048576 /dev/zero >&2; printf ' ready \\n'")
+    #expect(result.lines == [" ready "])
+    #expect(result.diagnostics == Data(repeating: 0, count: 1048576))
+}
+
+@Test func drainsSimultaneousLargeStreams() throws {
+    let result = try runCommand("/usr/bin/head -c 1048576 /dev/zero >&2 & /usr/bin/head -c 1048576 /dev/zero; wait")
+    #expect(result.lines == [String(repeating: "\0", count: 1048576)])
+    #expect(result.diagnostics == Data(repeating: 0, count: 1048576))
+}
+
+@Test func emptyCommandOutput() throws {
+    let result = try runCommand(":")
+    #expect(result.lines.isEmpty)
+    #expect(result.diagnostics.isEmpty)
+}
+
+@Test func failedCommandForwardsDiagnostics() throws {
+    let result = try runCommand("printf 'ignored'; printf 'failure\\n' >&2; exit 7")
+    #expect(result.lines == ["ERROR"])
+    #expect(result.diagnostics == Data("failure\n".utf8))
+}
+
+@Test func shellEnvironmentAndWhitespaceArePreserved() throws {
+    let result = try runCommand("printf ' %s \\n\\nlast\\n' \"$BAR_RUNNER_TEST\"; test -n \"$PATH\"", env: ["BAR_RUNNER_TEST": "value"])
+    #expect(result.lines == [" value ", "", "last"])
 }