added first createReadStream test

test/create-read-stream.js

@@ -0,0 +1,32 @@
+var tape = require('tape');
+var Cache = require('..');
+var MemDB = require('memdb');
+var through = require('through');
+
+function test (name, fn) {
+  tape.test(name, function (t) {
+    var source = MemDB();
+    var cache = MemDB();
+    var db = Cache(source, cache);
+    fn(t, db, source, cache);
+  });
+}
+
+test('reads data from source', function (t, db, source, cache) {
+  t.plan(4);
+
+  source.put('foo', 'bar', function (err) {
+    t.error(err);
+    db.createReadStream().pipe(through(write, end));
+
+    function write (kv) {
+      t.equal(kv.key, 'foo');
+      t.equal(kv.value, 'bar');
+    }
+
+    function end () {
+      t.ok(true, 'ended');
+    }
+  });
+});
+