Fix bug reading default value for combine_output

The default should be set to true so we maintain backwards.
compatibility.
readconfig.go was altered due to bug reading default value. This was
tested by adding unit tests to readconfig_test.go for positive and
negative scenarios.

Signed-off-by: Alex Ellis (VMware) <alexellis2@gmail.com>

watchdog/Dockerfile

@@ -2,11 +2,10 @@ FROM golang:1.8.5
 RUN mkdir -p /go/src/github.com/openfaas/faas/watchdog
 WORKDIR /go/src/github.com/openfaas/faas/watchdog
 
-COPY main.go        .
-COPY readconfig.go  .
-COPY config_test.go .
+COPY main.go            .
+COPY readconfig.go      .
+COPY readconfig_test.go .
 COPY requesthandler_test.go .
-
 COPY types types
 
 # Run a gofmt and exclude all vendored code.

watchdog/readconfig.go

@@ -87,7 +87,7 @@ func (ReadConfig) Read(hasEnv HasEnv) WatchdogConfig {
 
 	cfg.contentType = hasEnv.Getenv("content_type")
 
-	if isBoolValueSet("combine_output") {
+	if isBoolValueSet(hasEnv.Getenv("combine_output")) {
 		cfg.combineOutput = parseBoolValue(hasEnv.Getenv("combine_output"))
 	}
 

watchdog/readconfig_test.go

@@ -26,6 +26,31 @@ func (e EnvBucket) Setenv(key string, value string) {
 	e.Items[key] = value
 }
 
+func TestRead_CombineOutput_DefaultTrue(t *testing.T) {
+	defaults := NewEnvBucket()
+	readConfig := ReadConfig{}
+
+	config := readConfig.Read(defaults)
+	want := true
+	if config.combineOutput != want {
+		t.Logf("combineOutput error, want: %v, got: %v", want, config.combineOutput)
+		t.Fail()
+	}
+}
+
+func TestRead_CombineOutput_OverrideFalse(t *testing.T) {
+	defaults := NewEnvBucket()
+	readConfig := ReadConfig{}
+	defaults.Setenv("combine_output", "false")
+
+	config := readConfig.Read(defaults)
+	want := false
+	if config.combineOutput != want {
+		t.Logf("combineOutput error, want: %v, got: %v", want, config.combineOutput)
+		t.Fail()
+	}
+}
+
 func TestRead_CgiHeaders_OverrideFalse(t *testing.T) {
 	defaults := NewEnvBucket()
 	readConfig := ReadConfig{}