Add json output format

Closes #1

src/args.rs

@@ -112,7 +112,8 @@ pub struct Arguments {
         value_name = "pretty|terse|json",
         help = "Configure formatting of output: \n\
             - pretty = Print verbose output\n\
-            - terse = Display one character per test\n",
+            - terse = Display one character per test\n\
+            - json = Print json events\n",
     )]
     pub format: Option<FormatSetting>,
 
@@ -176,6 +177,9 @@ pub enum FormatSetting {
 
     /// One character per test. Usefull for test suites with many tests.
     Terse,
+
+    /// Json output
+    Json,
 }
 
 impl Default for FormatSetting {

src/lib.rs

@@ -451,7 +451,7 @@ pub fn run(args: &Arguments, mut tests: Vec<Trial>) -> Conclusion {
 
     let mut failed_tests = Vec::new();
     let mut handle_outcome = |outcome: Outcome, test: TestInfo, printer: &mut Printer| {
-        printer.print_single_outcome(&outcome);
+        printer.print_single_outcome(&test, &outcome);
 
         // Handle outcome
         match outcome {

src/printer.rs

@@ -92,6 +92,12 @@ impl Printer {
                 writeln!(self.out).unwrap();
                 writeln!(self.out, "running {} test{}", num_tests, plural_s).unwrap();
             }
+            FormatSetting::Json => writeln!(
+                self.out,
+                "{{ \"type\": \"suite\", \"event\": \"started\", \"test_count\": {} }}",
+                num_tests
+            )
+            .unwrap(),
         }
     }
 
@@ -121,12 +127,20 @@ impl Printer {
                 // In terse mode, nothing is printed before the job. Only
                 // `print_single_outcome` prints one character.
             }
+            FormatSetting::Json => {
+                writeln!(
+                    self.out,
+                    "{{ \"type\": \"test\", \"event\": \"started\", \"name\": \"{}\" }}",
+                    name
+                )
+                .unwrap();
+            }
         }
     }
 
     /// Prints the outcome of a single tests. `ok` or `FAILED` in pretty mode
     /// and `.` or `F` in terse mode.
-    pub(crate) fn print_single_outcome(&mut self, outcome: &Outcome) {
+    pub(crate) fn print_single_outcome(&mut self, info: &TestInfo, outcome: &Outcome) {
         match self.format {
             FormatSetting::Pretty => {
                 self.print_outcome_pretty(outcome);
@@ -150,6 +164,34 @@ impl Printer {
                 write!(self.out, "{}", c).unwrap();
                 self.out.reset().unwrap();
             }
+            FormatSetting::Json => {
+                if let Outcome::Measured(Measurement { avg, variance }) = outcome {
+                    writeln!(
+                        self.out,
+                        r#"{{ "type": "bench", "name": "{}", "median": {}, "deviation": {} }}"#,
+                        info.name, avg, variance
+                    )
+                    .unwrap();
+                } else {
+                    writeln!(
+                        self.out,
+                        r#"{{ "type": "test", "name": "{}", "event": "{}"{} }}"#,
+                        info.name,
+                        match outcome {
+                            Outcome::Passed => "ok",
+                            Outcome::Failed(_) => "failed",
+                            Outcome::Ignored => "ignored",
+                            Outcome::Measured(_) => unreachable!(),
+                        },
+                        match outcome {
+                            Outcome::Failed(Failed { msg: Some(msg) }) =>
+                                format!(r#", "stdout": "Error: \"{}\"\n""#, msg.escape_default()),
+                            _ => "".into(),
+                        }
+                    )
+                    .unwrap();
+                }
+            }
         }
     }
 
@@ -179,6 +221,20 @@ impl Printer {
                 ).unwrap();
                 writeln!(self.out).unwrap();
             }
+            FormatSetting::Json => {
+                writeln!(
+                    self.out,
+                    "{{ \"type\": \"suite\", \"event\": \"{}\", \"passed\": {}, \"failed\": {}, \"ignored\": {}, \"measured\": {}, \"filtered_out\": {}, \"exec_time\": {} }}",
+                    if conclusion.num_failed > 0 { "failed" } else { "ok" },
+                    conclusion.num_passed,
+                    conclusion.num_failed,
+                    conclusion.num_ignored,
+                    conclusion.num_measured,
+                    conclusion.num_filtered_out,
+                    execution_time.as_secs_f64()
+                )
+                .unwrap();
+            }
         }
     }
 
@@ -221,6 +277,9 @@ impl Printer {
     /// Prints a list of failed tests with their messages. This is only called
     /// if there were any failures.
     pub(crate) fn print_failures(&mut self, fails: &[(TestInfo, Option<String>)]) {
+        if self.format == FormatSetting::Json {
+            return;
+        }
         writeln!(self.out).unwrap();
         writeln!(self.out, "failures:").unwrap();
         writeln!(self.out).unwrap();

tests/common/mod.rs

@@ -97,6 +97,11 @@ macro_rules! assert_log {
             }
         }
 
+        if let Some(pos) = actual.rfind("\"exec_time\":") {
+            actual.truncate(pos);
+            actual.push_str("\"exec_time\": 0.000000000 }");
+        }
+
         assert_eq!(actual, expected);
     };
 }

tests/mixed_bag.rs

@@ -597,3 +597,56 @@ fn terse_output() {
             finished in 0.00s
     ");
 }
+
+#[test]
+fn json_output() {
+    let (c, out) = do_run(args(["--format", "json", "--test-threads", "1"]), tests());
+    assert_eq!(
+        c,
+        Conclusion {
+            num_filtered_out: 0,
+            num_passed: 4,
+            num_failed: 4,
+            num_ignored: 8,
+            num_measured: 0,
+        }
+    );
+
+    assert_log!(
+        out,
+        r#"{ "type": "suite", "event": "started", "test_count": 16 }
+{ "type": "test", "event": "started", "name": "cat" }
+{ "type": "test", "name": "cat", "event": "ok" }
+{ "type": "test", "event": "started", "name": "dog" }
+{ "type": "test", "name": "dog", "event": "failed", "stdout": "Error: \"was not a good boy\"\n" }
+{ "type": "test", "event": "started", "name": "fox" }
+{ "type": "test", "name": "fox", "event": "ok" }
+{ "type": "test", "event": "started", "name": "bunny" }
+{ "type": "test", "name": "bunny", "event": "failed", "stdout": "Error: \"jumped too high\"\n" }
+{ "type": "test", "event": "started", "name": "frog" }
+{ "type": "test", "name": "frog", "event": "ignored" }
+{ "type": "test", "event": "started", "name": "owl" }
+{ "type": "test", "name": "owl", "event": "ignored" }
+{ "type": "test", "event": "started", "name": "fly" }
+{ "type": "test", "name": "fly", "event": "ignored" }
+{ "type": "test", "event": "started", "name": "bear" }
+{ "type": "test", "name": "bear", "event": "ignored" }
+{ "type": "test", "event": "started", "name": "red" }
+{ "type": "test", "name": "red", "event": "ok" }
+{ "type": "test", "event": "started", "name": "blue" }
+{ "type": "test", "name": "blue", "event": "failed", "stdout": "Error: \"sky fell down\"\n" }
+{ "type": "test", "event": "started", "name": "yellow" }
+{ "type": "test", "name": "yellow", "event": "ok" }
+{ "type": "test", "event": "started", "name": "green" }
+{ "type": "test", "name": "green", "event": "failed", "stdout": "Error: \"was poisoned\"\n" }
+{ "type": "test", "event": "started", "name": "purple" }
+{ "type": "test", "name": "purple", "event": "ignored" }
+{ "type": "test", "event": "started", "name": "cyan" }
+{ "type": "test", "name": "cyan", "event": "ignored" }
+{ "type": "test", "event": "started", "name": "orange" }
+{ "type": "test", "name": "orange", "event": "ignored" }
+{ "type": "test", "event": "started", "name": "pink" }
+{ "type": "test", "name": "pink", "event": "ignored" }
+{ "type": "suite", "event": "failed", "passed": 4, "failed": 4, "ignored": 8, "measured": 0, "filtered_out": 0, "exec_time": 0.000000000 }"#
+    );
+}