Document JSON measurements and omit unavailable memory metrics

src/export/json.rs

@@ -32,3 +32,50 @@ impl Exporter for JsonExporter {
         Ok(output?)
     }
 }
+
+#[test]
+fn test_json_optional_memory() {
+    use crate::benchmark::measurement::{Measurement, Measurements};
+    use crate::quantity::{byte, Information};
+    use serde_json::json;
+
+    for (memory, expected_memory) in [
+        (None, None),
+        (
+            Some(Information::new::<byte>(0.0)),
+            Some(json!({"value": 0.0, "unit": "byte"})),
+        ),
+        (
+            Some(Information::new::<byte>(1024.0)),
+            Some(json!({"value": 1024.0, "unit": "byte"})),
+        ),
+    ] {
+        let result = BenchmarkResult {
+            command: "example".into(),
+            measurements: Measurements::new(vec![Measurement {
+                peak_memory_usage: memory,
+                ..Measurement::default()
+            }]),
+            ..BenchmarkResult::default()
+        };
+        let output = JsonExporter::default()
+            .serialize(&[result], None, SortOrder::Command)
+            .unwrap();
+        let actual: serde_json::Value = serde_json::from_slice(&output).unwrap();
+        let mut expected = json!({
+            "results": [{
+                "command": "example",
+                "measurements": [{
+                    "time_wall_clock": {"value": 0.0, "unit": "second"},
+                    "time_user": {"value": 0.0, "unit": "second"},
+                    "time_system": {"value": 0.0, "unit": "second"},
+                    "exit_code": 0
+                }]
+            }]
+        });
+        if let Some(memory) = expected_memory {
+            expected["results"][0]["measurements"][0]["peak_memory_usage"] = memory;
+        }
+        assert_eq!(actual, expected);
+    }
+}