Add a "check-config" command to validate config files & tests for it

tests/integrations/check_config.rs

@@ -0,0 +1,95 @@
+use std::{
+    path::{Path, PathBuf},
+    process::Output,
+};
+
+use assert_cmd::Command;
+
+type TestError = Box<dyn std::error::Error>;
+type TestResult = Result<(), TestError>;
+
+fn fixture_path<P>(name: P) -> PathBuf
+where
+    P: AsRef<Path>,
+{
+    PathBuf::from("tests/integrations/fixtures/check_config").join(name)
+}
+
+fn run<P>(file: P) -> Result<Output, TestError>
+where
+    P: AsRef<Path>,
+{
+    Command::cargo_bin("grapevine")?
+        .args(["check-config", "--log-format=json", "-c"])
+        .arg(fixture_path(file))
+        .output()
+        .map_err(Into::into)
+}
+
+macro_rules! make_snapshot_test {
+    ($name:ident, $description:expr, $fixture_name:expr $(,)?) => {
+        #[test]
+        fn $name() -> TestResult {
+            let output = run($fixture_name)?;
+
+            let stdout = String::from_utf8(output.stdout)?;
+            let stderr = String::from_utf8(output.stderr)?;
+            let status_code = output.status.code();
+
+            insta::with_settings!({
+                description => $description,
+                omit_expression => true,
+                snapshot_suffix => "stdout",
+            }, {
+                insta::assert_snapshot!(stdout);
+            });
+
+            let stderr_parse = serde_json::Deserializer::from_str(&stderr)
+                .into_iter::<serde_json::Value>()
+                .collect::<Result<Vec<_>, _>>();
+            insta::with_settings!({
+                description => $description,
+                omit_expression => true,
+                snapshot_suffix => "stderr",
+            }, {
+                if let Ok(stderr_json) = stderr_parse {
+                    insta::assert_json_snapshot!(stderr_json, {
+                        ".*.timestamp" => "[timestamp]"
+                    });
+                } else {
+                    insta::assert_snapshot!(stderr);
+                }
+            });
+
+            insta::with_settings!({
+                description => $description,
+                omit_expression => true,
+                snapshot_suffix => "status_code",
+            }, {
+                insta::assert_debug_snapshot!(status_code);
+            });
+
+            Ok(())
+        }
+    };
+}
+
+make_snapshot_test!(valid_config, "A normal config is valid", "valid.toml");
+
+make_snapshot_test!(
+    minimal_valid_config,
+    "A configuration containing only the required keys is valid",
+    "minimal-valid.toml",
+);
+
+make_snapshot_test!(
+    invalid_keys,
+    "A config with invalid keys fails",
+    "invalid-keys.toml",
+);
+
+make_snapshot_test!(
+    invalid_values,
+    "A config with invalid values fails",
+    "invalid-values.toml",
+);