Merge pull request #3 from kalafut/master

Add SetOutput function to change message output destination

is.go

@@ -1,10 +1,14 @@
 package is
 
 import (
+	"io"
 	"log"
+	"os"
 	"testing"
 )
 
+var output io.Writer = os.Stdout
+
 // Is provides methods that leverage the existing testing capabilities found
 // in the Go test framework. The methods provided allow for a more natural,
 // efficient and expressive approach to writing tests. The goal is to write
@@ -146,3 +150,10 @@ func (is *Is) NotZero(o interface{}) {
 		fail(is, "expected object '%s' not to be zero value", objectTypeName(o))
 	}
 }
+
+// SetOutput changes the message output Writer from the default (os.Stdout).
+// This may be useful if the application under test takes over the console, or
+// if logging to a file is desired.
+func SetOutput(w io.Writer) {
+	output = w
+}

workers.go

@@ -73,9 +73,9 @@ var fail = failDefault
 
 // failDefault is the default failure function.
 func failDefault(is *Is, format string, args ...interface{}) {
-	fmt.Print(decorate(fmt.Sprintf(format, args...)))
+	fmt.Fprint(output, decorate(fmt.Sprintf(format, args...)))
 	if len(is.failFormat) != 0 {
-		fmt.Printf(is.failFormat+"\n", is.failArgs...)
+		fmt.Fprintf(output, is.failFormat+"\n", is.failArgs...)
 	}
 	is.TB.FailNow()
 }