diff --git a/data-snapshots/geolite2_country.mmdb b/data-snapshots/geolite2_country.mmdb
new file mode 100644
index 0000000..7e8a998
Binary files /dev/null and b/data-snapshots/geolite2_country.mmdb differ
diff --git a/geoip.go b/geoip.go
index 9d67241..542d55a 100644
--- a/geoip.go
+++ b/geoip.go
@@ -101,7 +101,7 @@ func (a *GeoIP2AnnotatorFactory) AddFlags(flags *flag.FlagSet) {
 	flags.StringVar(&a.Language, "geoip2-language", "en",
 		"what language geoip2 database is in")
 	flags.StringVar(&a.RawInclude, "geoip2-fields", "*",
-		"city, continent, country, location, postal, registered_country, subdivisions, traits")
+		"comma-separated list of output fields to include, use '*' for all: city, continent, country, location, postal, registered_country, subdivisions, traits")
 	flags.IntVar(&a.Threads, "geoip2-threads", 5, "how many geoIP processing threads to use")
 }
 
diff --git a/geoip_test.go b/geoip_test.go
new file mode 100644
index 0000000..174df95
--- /dev/null
+++ b/geoip_test.go
@@ -0,0 +1,112 @@
+/*
+ * ZAnnotate Copyright 2025 Regents of the University of Michigan
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy
+ * of the License at http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+ * implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+package zannotate
+
+import (
+	"net"
+	"reflect"
+	"testing"
+)
+
+func TestGeoIPAnnotator(t *testing.T) {
+	tests := []struct {
+		testName       string
+		ipAddr         net.IP
+		expectedResult *GeoIP2Output
+	}{
+		{
+			testName: "Positive Test Case, IPv4",
+			ipAddr:   net.ParseIP("1.2.3.4"),
+			expectedResult: &GeoIP2Output{
+				City: &GeoIP2City{},
+				Country: &GeoIP2Country{
+					Name:      "Australia",
+					Code:      "AU",
+					GeoNameId: 2077456,
+				},
+				Continent: &GeoIP2Country{
+					Name:      "Oceania",
+					Code:      "OC",
+					GeoNameId: 6255151,
+				},
+				Postal:             &GeoIP2Postal{},
+				LatLong:            &GeoIP2LatLong{},
+				RepresentedCountry: &GeoIP2Country{},
+				RegisteredCountry: &GeoIP2Country{
+					Name:      "Australia",
+					Code:      "AU",
+					GeoNameId: 2077456,
+				},
+				Traits: &GeoIP2Traits{},
+			},
+		}, {
+			testName: "Positive Test Case, IPv6",
+			ipAddr:   net.ParseIP("2606:4700:4700::1111"),
+			expectedResult: &GeoIP2Output{
+				City:               &GeoIP2City{},
+				Country:            &GeoIP2Country{},
+				Continent:          &GeoIP2Country{},
+				Postal:             &GeoIP2Postal{},
+				LatLong:            &GeoIP2LatLong{},
+				RepresentedCountry: &GeoIP2Country{},
+				RegisteredCountry: &GeoIP2Country{
+					Name:      "United States",
+					Code:      "US",
+					GeoNameId: 6252001,
+				},
+				Traits: &GeoIP2Traits{},
+			},
+		}, {
+			testName: "Negative Test Case, Private IP",
+			ipAddr:   net.ParseIP("192.168.0.1"),
+			expectedResult: &GeoIP2Output{
+				City:               &GeoIP2City{},
+				Country:            &GeoIP2Country{},
+				Continent:          &GeoIP2Country{},
+				Postal:             &GeoIP2Postal{},
+				LatLong:            &GeoIP2LatLong{},
+				RepresentedCountry: &GeoIP2Country{},
+				RegisteredCountry:  &GeoIP2Country{},
+				Traits:             &GeoIP2Traits{},
+			},
+		},
+	}
+	factory := &GeoIP2AnnotatorFactory{
+		Path:       "./data-snapshots/geolite2_country.mmdb",
+		Mode:       "mmap",
+		Language:   "en",
+		RawInclude: "*",
+	}
+	err := factory.Initialize(nil)
+	if err != nil {
+		t.Fatalf("Failed to initialize factory: %v", err)
+	}
+	for _, tt := range tests {
+		t.Run(tt.testName, func(t *testing.T) {
+			annotator := factory.MakeAnnotator(0).(*GeoIP2Annotator)
+			err = annotator.Initialize()
+			if err != nil {
+				t.Fatalf("Failed to initialize annotator: %v", err)
+			}
+			result := annotator.Annotate(tt.ipAddr)
+			if tt.expectedResult == nil && result == nil {
+				return // pass
+			}
+			if !reflect.DeepEqual(result, tt.expectedResult) {
+				t.Errorf("Annotating IP %s gave = %v; expected: %v", tt.ipAddr, result, tt.expectedResult)
+			}
+		})
+	}
+}