PLT-6090 adding ability to read license file from disk (#5895)

* PLT-6090 adding ability to read license file from disk

* Fixing unit test that fails only sometimes

* Fixing test that fails randomly

utils/license_test.go

@@ -66,3 +66,31 @@ func TestClientLicenseEtag(t *testing.T) {
 		t.Fatal("etags should not match")
 	}
 }
+
+func TestGetLicenseFileLocation(t *testing.T) {
+	fileName := GetLicenseFileLocation("")
+	if len(fileName) == 0 {
+		t.Fatal("invalid default file name")
+	}
+
+	fileName = GetLicenseFileLocation("mattermost.mattermost-license")
+	if fileName != "mattermost.mattermost-license" {
+		t.Fatal("invalid file name")
+	}
+}
+
+func TestGetLicenseFileFromDisk(t *testing.T) {
+	fileBytes := GetLicenseFileFromDisk("thisfileshouldnotexist.mattermost-license")
+	if len(fileBytes) > 0 {
+		t.Fatal("invalid bytes")
+	}
+
+	fileBytes = GetLicenseFileFromDisk(FindConfigFile("config.json"))
+	if len(fileBytes) == 0 { // a valid bytes but should be a fail license
+		t.Fatal("invalid bytes")
+	}
+
+	if success, _ := ValidateLicense(fileBytes); success {
+		t.Fatal("should have been an invalid file")
+	}
+}