Update tests to reflect new b64 behaviour

test/b64.js

@@ -6,15 +6,18 @@ test('b64 is a function', t => {
 	t.is(typeof b64, 'function');
 });
 
-test('b64 calls b64[opts.method]', async t => {
-	const encodeResult = await b64(values.buffer, { method: 'encode' });
-	const decodeResult = await b64(values.base64, { method: 'decode' });
-	t.is(encodeResult, values.base64);
-	t.true(decodeResult instanceof Buffer);
-	t.is(decodeResult.toString(), values.string);
+test('b64 calls b64.encode on buffers', async t => {
+	const result = await b64(values.buffer);
+	t.is(result, values.base64);
 });
 
-test('b64 rejects Promise if method is not \'encode\' or \'decode\'', async t => {
-	const error = await t.throws(b64(values.buffer));
-	t.is(error.message, 'opts.method must be \'encode\' or \'decode\'.');
+test('b64 calls b64.decode on strings', async t => {
+	const result = await b64(values.base64);
+	t.true(result instanceof Buffer);
+	t.is(result.toString(), values.string);
+});
+
+test('b64 rejects Promise if input is not a buffer or string', async t => {
+	const error = await t.throws(b64(0));
+	t.is(error.message, 'input must be a buffer or string');
 });