Add test for withMetadata convenience function

Author: gabbifish

Tests/LoggingTests/LoggingTest.swift

@@ -357,6 +357,25 @@ class LoggingTest: XCTestCase {
                                                    "nested-list": ["l1str", ["l2str1", "l2str2"]]])
     }
 
+    func testWithMetadata() {
+        let testLogging = TestLogging()
+        LoggingSystem.bootstrapInternal { testLogging.make(label: $0) }
+
+        var logger = Logger(label: "\(#function)")
+        let metadata: Logger.Metadata = [
+            "foo": ["bar", "buz"],
+            "empty-list": [],
+            "nested-list": ["l1str", ["l2str1", "l2str2"]]
+        ]
+        logger.withMetadata(metadata: metadata)
+        logger.info("hello world!")
+        testLogging.history.assertExist(level: .info,
+                                        message: "hello world!",
+                                        metadata: ["foo": ["bar", "buz"],
+                                                   "empty-list": [],
+                                                   "nested-list": ["l1str", ["l2str1", "l2str2"]]])
+    }
+
     // Example of custom "box" which may be used to implement "render at most once" semantics
     // Not thread-safe, thus should not be shared across threads.
     internal final class LazyMetadataBox: CustomStringConvertible {