Fix several bugs in minecraft input (#2970)

plugins/inputs/minecraft/rcon_disconnect_error_test.go

@@ -0,0 +1,36 @@
+package minecraft
+
+import (
+	"errors"
+	"testing"
+)
+
+type MockRCONProducer struct {
+	Err error
+}
+
+func (m *MockRCONProducer) newClient() (RCONClient, error) {
+	return nil, m.Err
+}
+
+func TestRCONErrorHandling(t *testing.T) {
+	m := &MockRCONProducer{
+		Err: errors.New("Error: failed connection"),
+	}
+	c := &RCON{
+		Server:   "craftstuff.com",
+		Port:     "2222",
+		Password: "pass",
+		//Force fetching of new client
+		client: nil,
+	}
+
+	_, err := c.Gather(m)
+	if err == nil {
+		t.Errorf("Error nil, unexpected result")
+	}
+
+	if c.client != nil {
+		t.Fatal("c.client should be nil, unexpected result")
+	}
+}