diff --git a/Sources/LoggingLoki/LokiLogProcessor.swift b/Sources/LoggingLoki/LokiLogProcessor.swift
index f11072e..5f92bd8 100644
--- a/Sources/LoggingLoki/LokiLogProcessor.swift
+++ b/Sources/LoggingLoki/LokiLogProcessor.swift
@@ -193,25 +193,28 @@ public struct LokiLogProcessor<Clock: _Concurrency.Clock>: Sendable, Service whe
     }
 
     func addEntryToBatch(_ log: LokiLog, with labels: [String: String]) {
-        let _log: LokiLog.Transport
+        let log = makeLog(log)
+        continuation.yield((log, labels))
+    }
+
+    func makeLog(_ log: LokiLog) -> LokiLog.Transport {
         switch configuration.metadataFormat.code {
         case .logfmt:
             var line = "[\(log.level.rawValue.uppercased())] message=\"\(log.message)\""
             if let metadata = prettify(log.metadata) {
                 line += " \(metadata)"
             }
-            _log = .init(timestamp: .init(), line: line)
+            return .init(timestamp: .init(), line: line)
         case .structured:
-            _log = .init(
+            return .init(
                 timestamp: .init(),
                 line: "[\(log.level.rawValue.uppercased())] \(log.message)",
                 metadata: log.metadata.mapValues(\.description)
             )
         case .custom(let customFormatter):
             let line = customFormatter(log.level, log.message, log.metadata)
-            _log = .init(timestamp: .init(), line: line)
+            return .init(timestamp: .init(), line: line)
         }
-        continuation.yield((_log, labels))
     }
 
     private func sendBatch(_ batch: Batch<Clock>) async throws {
diff --git a/Tests/LoggingLokiTests/LokiLogProcessorTests.swift b/Tests/LoggingLokiTests/LokiLogProcessorTests.swift
new file mode 100644
index 0000000..d927696
--- /dev/null
+++ b/Tests/LoggingLokiTests/LokiLogProcessorTests.swift
@@ -0,0 +1,43 @@
+import XCTest
+@testable import LoggingLoki
+
+final class LokiLogProcessorTests: XCTestCase {
+    func testLogFmtFormat() {
+        let configuration = LokiLogProcessorConfiguration(
+            lokiURL: "http://localhost:3100",
+            metadataFormat: .logfmt
+        )
+        let processor = LokiLogProcessor(configuration: configuration)
+        let raw = LokiLog(
+            timestamp: .init(),
+            level: .info,
+            message: "My log message",
+            metadata: ["basic_key": "basic_value", "additional_key": "value with whitespace"]
+        )
+        let formatted = processor.makeLog(raw)
+        XCTAssertNil(formatted.metadata)
+        XCTAssertTrue(formatted.line.starts(with: "[INFO] "))
+        XCTAssertTrue(formatted.line.contains("basic_key=basic_value"))
+        XCTAssertTrue(formatted.line.contains(#"additional_key="value with whitespace""#))
+        XCTAssertTrue(formatted.line.contains(#"message="My log message""#))
+    }
+
+    func testCustomFormat() {
+        let configuration = LokiLogProcessorConfiguration(
+            lokiURL: "http://localhost:3100",
+            metadataFormat: .custom({ level, message, metadata in
+                "\(level.rawValue.uppercased()): \(message) \(metadata)"
+            })
+        )
+        let processor = LokiLogProcessor(configuration: configuration)
+        let raw = LokiLog(
+            timestamp: .init(),
+            level: .info,
+            message: "My log message",
+            metadata: ["basic_key": "basic_value", "additional_key": "value with whitespace"]
+        )
+        let formatted = processor.makeLog(raw)
+        XCTAssertNil(formatted.metadata)
+        XCTAssertEqual(formatted.line, #"INFO: My log message ["basic_key": basic_value, "additional_key": value with whitespace]"#)
+    }
+}