feat: isLogger and ensureLogger utils

ensure-logger.js

@@ -0,0 +1,9 @@
+"use strict";
+
+var toShortString = require("es5-ext/to-short-string-representation")
+  , isLogger      = require("./is-logger");
+
+module.exports = function (logger) {
+	if (isLogger(logger)) return logger;
+	throw new TypeError(toShortString(logger) + " is not a logger");
+};

is-logger.js

@@ -0,0 +1,9 @@
+"use strict";
+
+var isPlainFunction = require("es5-ext/object/is-plain-function");
+
+module.exports = function (logger) {
+	if (!isPlainFunction(logger)) return false;
+	if (typeof logger.level !== "string") return false;
+	return typeof logger.isNamespaceInitialized === "function";
+};

test/ensure-logger.js

@@ -0,0 +1,17 @@
+"use strict";
+
+var test         = require("tape")
+  , log          = require("../")
+  , ensureLogger = require("../ensure-logger");
+
+test("Ensure Logger", function (t) {
+	t.equal(ensureLogger(log), log, "Should return logger when logger is an argument");
+	t.throws(
+		function () {
+			ensureLogger(function () { return "foo"; });
+		},
+		TypeError,
+		"Should throw on non logger values"
+	);
+	t.end();
+});

test/is-logger.js

@@ -0,0 +1,15 @@
+"use strict";
+
+var test     = require("tape")
+  , log      = require("../")
+  , isLogger = require("../is-logger");
+
+test("Is Logger", function (t) {
+	t.equal(isLogger(log), true, "Should return true on logger");
+	t.equal(isLogger(), false, "Should return false on non-value");
+	t.equal(
+		isLogger(function () { return "foo"; }), false,
+		"Should return false on non-logger function "
+	);
+	t.end();
+});