using diffy to show diff when showing output (#14)

fbt_lib/src/run.rs

@@ -70,6 +70,42 @@ pub fn main() -> Option<i32> {
                     std::str::from_utf8(&output.stderr).unwrap_or("failed to decode")
                 );
             }
+            Err(crate::Failure::StdoutMismatch { expected, output }) => {
+                any_failed = true;
+                println!(
+                    "{}: {} {} (stdout mismatch)",
+                    case.id.blue(),
+                    "FAILED".red(),
+                    duration,
+                );
+                let stdout = std::str::from_utf8(&output.stdout).unwrap_or("failed to decode");
+                println!("stdout:\n\n{}\n", stdout);
+                println!(
+                    "diff:\n\n{}\n",
+                    diffy::create_patch(
+                        (expected.to_owned() + "\n").as_str(),
+                        (stdout.to_owned() + "\n").as_str()
+                    )
+                );
+            }
+            Err(crate::Failure::StderrMismatch { expected, output }) => {
+                any_failed = true;
+                println!(
+                    "{}: {} {} (stderr mismatch)",
+                    case.id.blue(),
+                    "FAILED".red(),
+                    duration,
+                );
+                let stderr = std::str::from_utf8(&output.stderr).unwrap_or("failed to decode");
+                println!("stderr:\n\n{}\n", stderr);
+                println!(
+                    "diff:\n\n{}\n",
+                    diffy::create_patch(
+                        (expected.to_owned() + "\n").as_str(),
+                        (stderr.to_owned() + "\n").as_str()
+                    )
+                );
+            }
             Err(e) => {
                 any_failed = true;
                 println!(

tests/03_failing_fbt_tests/cmd.p1

@@ -6,6 +6,33 @@ In this test we check for failing conditions.
 
 -- stdout:
 
-01_basic: FAILED  (StdoutMismatch { expected: "hello world", output: Output { status: ExitStatus(ExitStatus(0)), stdout: "hello there", stderr: "" } })
+01_stdout_mismatch: FAILED  (stdout mismatch)
+stdout:
+
+hello there
+
+diff:
+
+\--- original
++++ modified
+@@ -1 +1 @@
+-hello world
++hello there
+
+
 02_output_mismatch: SKIPPED (output not yet implemented)
+03_stderr_mismatch: FAILED  (stderr mismatch)
+stderr:
+
+hello there
+
+diff:
+
+\--- original
++++ modified
+@@ -1 +1 @@
+-hello world
++hello there
+
+
 

tests/03_failing_fbt_tests/input/tests/03_stderr_mismatch/cmd.p1

@@ -0,0 +1,6 @@
+-- fbt:
+cmd: cat one 1>&2
+
+-- stderr:
+
+hello world

tests/03_failing_fbt_tests/input/tests/03_stderr_mismatch/input/one

@@ -0,0 +1 @@
+hello there