Add integration test for cargo nextest run on the example test harness

Cargo.toml

@@ -20,3 +20,7 @@ walkdir = "2.5.0"
 [[test]]
 name = "example"
 harness = false
+
+[[test]]
+name = "run_example"
+harness = true

tests/run_example.rs

@@ -0,0 +1,39 @@
+#[test]
+fn run_example() {
+    let output = std::process::Command::new("cargo")
+        .args(["nextest", "run", "--test=example"])
+        .env("DATATEST_FULL_SCAN_FORBIDDEN", "1")
+        .output()
+        .expect("Failed to run `cargo nextest`");
+
+    // It's a pain to make assertions on byte slices (even a subslice check isn't easy)
+    // and it's also difficult to print nice error messages. So we just assume all
+    // nextest output will be utf8 and convert it.
+    let stderr = std::str::from_utf8(&output.stderr).expect("Failed to convert stderr to utf-8");
+
+    assert!(
+        output.status.success(),
+        "Command failed (exit status: {}, stderr: {stderr})",
+        output.status
+    );
+
+    let lines: &[&str] = &[
+        "datatest-stable::example test_artifact::::colon::dir/::.txt",
+        "datatest-stable::example test_artifact::::colon::dir/a.txt",
+        "datatest-stable::example test_artifact::a.txt",
+        "datatest-stable::example test_artifact_utf8::::colon::dir/::.txt",
+        "datatest-stable::example test_artifact::b.txt",
+        "datatest-stable::example test_artifact_utf8::::colon::dir/a.txt",
+        "datatest-stable::example test_artifact_utf8::a.txt",
+        "datatest-stable::example test_artifact_utf8::c.skip.txt",
+        "datatest-stable::example test_artifact_utf8::b.txt",
+        "9 tests run: 9 passed, 0 skipped",
+    ];
+
+    for line in lines {
+        assert!(
+            stderr.contains(line),
+            "Expected to find substring\n  {line}\nin stderr\n  {stderr}",
+        );
+    }
+}