Adds fctesting.TestWriter

TestWriter allows for mocking along with other functionality, such as
syncing when to look at the contents of a writer in the event of
goroutines

Signed-off-by: xibz <[email protected]>

Author: xibz

fctesting/test_writer.go

@@ -0,0 +1,12 @@
+package fctesting
+
+// TestWriter is used to mock out writing and/or do other things such as
+// syncing when to do assertions in the event that a writer is used in a
+// goroutine
+type TestWriter struct {
+	WriteFn func([]byte) (int, error)
+}
+
+func (w *TestWriter) Write(b []byte) (int, error) {
+	return w.WriteFn(b)
+}