Moved validation into configuration and added unit tests.

bin/serve/main.go

@@ -133,26 +133,6 @@ func main() {
 		log.Fatalf("While loading configuration got %v", err)
 	}
 
-	// If HTTPS is to be used, verify both TLS_* environment variables are set.
-	if 0 < len(config.Get.TLSCert) || 0 < len(config.Get.TLSKey) {
-		if 0 == len(config.Get.TLSCert) || 0 == len(config.Get.TLSKey) {
-			log.Fatalln(
-				"If value for environment variable 'TLS_CERT' or 'TLS_KEY' is set " +
-					"then value for environment variable 'TLS_KEY' or 'TLS_CERT' must " +
-					"also be set.",
-			)
-		}
-	}
-
-	// If the URL path prefix is to be used, verify it is properly formatted.
-	if 0 < len(config.Get.URLPrefix) &&
-		(!strings.HasPrefix(config.Get.URLPrefix, "/") || strings.HasSuffix(config.Get.URLPrefix, "/")) {
-		log.Fatalln(
-			"Value for environment variable 'URL_PREFIX' must start " +
-				"with '/' and not end with '/'. Example: '/my/prefix'",
-		)
-	}
-
 	// Choose and set the appropriate, optimized static file serving function.
 	var handler http.HandlerFunc
 	if 0 == len(config.Get.URLPrefix) {

config/config.go

@@ -77,8 +77,9 @@ func Load(filename string) (err error) {
 	if err = yaml.Unmarshal(contents, &Get); nil != err {
 		return
 	}
+
 	overrideWithEnvVars()
-	return
+	return validate()
 }
 
 // overrideWithEnvVars the default values and the configuration file values.
@@ -93,6 +94,38 @@ func overrideWithEnvVars() {
 	Get.URLPrefix = envAsStr(urlPrefixKey, Get.URLPrefix)
 }
 
+// validate the configuration.
+func validate() error {
+	// If HTTPS is to be used, verify both TLS_* environment variables are set.
+	if 0 < len(Get.TLSCert) || 0 < len(Get.TLSKey) {
+		if 0 == len(Get.TLSCert) || 0 == len(Get.TLSKey) {
+			msg := "if value for either 'TLS_CERT' or 'TLS_KEY' is set then " +
+				"then value for the other must also be set (values are " +
+				"currently '%s' and '%s', respectively)"
+			return fmt.Errorf(msg, Get.TLSCert, Get.TLSKey)
+		}
+		if _, err := os.Stat(Get.TLSCert); nil != err {
+			msg := "value of TLS_CERT is set with filename '%s' that returns %v"
+			return fmt.Errorf(msg, err)
+		}
+		if _, err := os.Stat(Get.TLSKey); nil != err {
+			msg := "value of TLS_KEY is set with filename '%s' that returns %v"
+			return fmt.Errorf(msg, err)
+		}
+	}
+
+	// If the URL path prefix is to be used, verify it is properly formatted.
+	if 0 < len(Get.URLPrefix) &&
+		(!strings.HasPrefix(Get.URLPrefix, "/") || strings.HasSuffix(Get.URLPrefix, "/")) {
+		msg := "if value for 'URL_PREFIX' is set then the value must start " +
+			"with '/' and not end with '/' (current value of '%s' vs valid " +
+			"example of '/my/prefix'"
+		return fmt.Errorf(msg, Get.URLPrefix)
+	}
+
+	return nil
+}
+
 // envAsStr returns the value of the environment variable as a string if set.
 func envAsStr(key, fallback string) string {
 	if value := os.Getenv(key); "" != value {

config/config_test.go

@@ -135,6 +135,51 @@ func TestOverrideWithEnvvars(t *testing.T) {
 	equalStrings(t, phase, urlPrefixKey, testURLPrefix, Get.URLPrefix)
 }
 
+func TestValidate(t *testing.T) {
+	validPath := "config.go"
+	invalidPath := "should/never/exist.txt"
+	empty := ""
+	prefix := "/my/prefix"
+
+	testCases := []struct {
+		name    string
+		cert    string
+		key     string
+		prefix  string
+		isError bool
+	}{
+		{"Valid paths w/prefix", validPath, validPath, prefix, false},
+		{"Valid paths wo/prefix", validPath, validPath, empty, false},
+		{"Empty paths w/prefix", empty, empty, prefix, false},
+		{"Empty paths wo/prefix", empty, empty, empty, false},
+		{"Mixed paths w/prefix", empty, validPath, prefix, true},
+		{"Alt mixed paths w/prefix", validPath, empty, prefix, true},
+		{"Mixed paths wo/prefix", empty, validPath, empty, true},
+		{"Alt mixed paths wo/prefix", validPath, empty, empty, true},
+		{"Invalid cert w/prefix", invalidPath, validPath, prefix, true},
+		{"Invalid key w/prefix", validPath, invalidPath, prefix, true},
+		{"Invalid cert & key w/prefix", invalidPath, invalidPath, prefix, true},
+		{"Prefix missing leading /", empty, empty, "my/prefix", true},
+		{"Prefix with trailing /", empty, empty, "/my/prefix/", true},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			Get.TLSCert = tc.cert
+			Get.TLSKey = tc.key
+			Get.URLPrefix = tc.prefix
+			err := validate()
+			hasError := nil != err
+			if hasError && !tc.isError {
+				t.Errorf("Expected no error but got %v", err)
+			}
+			if !hasError && tc.isError {
+				t.Error("Expected an error but got no error")
+			}
+		})
+	}
+}
+
 func TestEnvAsStr(t *testing.T) {
 	sv := "STRING_VALUE"
 	fv := "FLOAT_VALUE"