diff --git a/src/nmea/gga.py b/src/nmea/gga.py
index bf3a1a9..fbedd78 100755
--- a/src/nmea/gga.py
+++ b/src/nmea/gga.py
@@ -77,7 +77,7 @@ def ggaDecode(nmeaStr, validate=False):
     """
     if validate:
         assert len(nmeaStr) >= 71
-        assert len(nmeaStr) <= 78
+        assert len(nmeaStr) <= 82
         assert nmeaStr[0] in ("$", "!")
         assert nmeaStr[3:6] == "GGA"
         # assert(nmea.isChecksumValid(nmeaStr))
diff --git a/tests/test_nmea/test_gga.py b/tests/test_nmea/test_gga.py
new file mode 100644
index 0000000..647cdf4
--- /dev/null
+++ b/tests/test_nmea/test_gga.py
@@ -0,0 +1,151 @@
+import calendar
+
+import pytest
+
+from nmea.gga import (
+    ggaDecode,
+    zdaDecode,
+    zdaDict2TIMESTAMP,
+    zdaEpochSeconds,
+)
+
+
+def test_zda_decode_valid():
+    """Test zdaDecode with a valid ZDA NMEA string."""
+    sentence = "$ZQZDA,110003.00,27,03,2006,-5,00*47"
+    decoded = zdaDecode(sentence)
+    assert decoded["timekeeper"] == "ZQ"
+    assert decoded["hour"] == 11
+    assert decoded["min"] == 0
+    assert decoded["sec"] == 3
+    assert decoded["hsec"] == 0
+    assert decoded["day"] == 27
+    assert decoded["mon"] == 3
+    assert decoded["year"] == 2006
+    assert decoded["localzonehour"] == -5
+    assert decoded["localzonemin"] == 0
+
+
+def test_zda_decode_invalid():
+    """Test zdaDecode with invalid ZDA strings."""
+    # Too short
+    with pytest.raises(AssertionError):
+        zdaDecode("$ZQZDA,110003")
+
+    # Incorrect starting character
+    with pytest.raises(AssertionError):
+        zdaDecode("ZQZDA,110003.00,27,03,2006,-5,00*47")
+
+    # Incorrect sentence type
+    with pytest.raises(AssertionError):
+        zdaDecode("$ZQGGA,110003.00,27,03,2006,-5,00*47")
+
+    # Missing dot in time
+    with pytest.raises(AssertionError):
+        zdaDecode("$ZQZDA,110003000,27,03,2006,-5,00*47")
+
+
+def test_zda_epoch_seconds():
+    """Test zdaEpochSeconds."""
+    sentence = "$ZQZDA,110003.00,27,03,2006,-5,00*47"
+    epoch = zdaEpochSeconds(sentence)
+    # The time is 2006-03-27 11:00:03 UTC
+    expected_epoch = calendar.timegm((2006, 3, 27, 11, 0, 3))
+    assert epoch == expected_epoch
+
+
+def test_zda_dict2timestamp():
+    """Test zdaDict2TIMESTAMP."""
+    zda_dict = {
+        "hour": 11,
+        "min": 0,
+        "hsec": 0,
+        "sec": 3,
+        "mon": 3,
+        "year": 2006,
+        "day": 27,
+        "timekeeper": "ZQ",
+        "localzonehour": -5,
+        "localzonemin": 0,
+    }
+    timestamp = zdaDict2TIMESTAMP(zda_dict)
+    assert timestamp == "2006-03-27 11:00:03"
+
+
+def test_gga_decode_valid():
+    """Test ggaDecode with a valid GGA NMEA string."""
+    sentence = "$GPGGA,152009.00,3652.48059177,N,07620.02018248,W,1,11,0.8,3.669,M,-34.579,M,,*57"
+    result = ggaDecode(sentence)
+
+    assert result["hour"] == "15"
+    assert result["min"] == "20"
+    assert result["sec"] == "09"
+    assert result["hsec"] == "00"
+    assert result["qual"] == 1
+    assert result["sats"] == 11
+    assert abs(result["horz_dilution"] - 0.8) < 1e-5
+    assert abs(result["alt"] - 3.669) < 1e-5
+    assert result["alt_units"] == "M"
+    assert abs(result["geoidal_sep"] - (-34.579)) < 1e-5
+    assert result["geoidal_sep_units"] == "M"
+    assert result["age"] is None  # Since it's empty in this case
+
+    # Test Lat / Lon calculations
+    # Latitude: 36 deg 52.48059177 min N = 36 + 52.48059177/60 = 36.8746765
+    assert abs(result["lat"] - 36.8746765295) < 1e-5
+    # Longitude: 076 deg 20.02018248 min W = -(76 + 20.02018248/60) = -76.3336697
+    assert abs(result["lon"] - (-76.333669708)) < 1e-5
+
+
+def test_gga_decode_south_east():
+    """Test ggaDecode with Southern Hemisphere and Eastern Hemisphere coordinates."""
+    # Dummy values modified for S and E
+    sentence = "$GPGGA,152009.00,3652.48059177,S,07620.02018248,E,1,11,0.8,3.669,M,-34.579,M,,*57"
+    result = ggaDecode(sentence)
+
+    # Latitude should be negative for South
+    assert result["lat"] < 0
+    assert abs(result["lat"] - (-36.8746765295)) < 1e-5
+
+    # Longitude should be positive for East
+    assert result["lon"] > 0
+    assert abs(result["lon"] - 76.333669708) < 1e-5
+
+
+def test_gga_decode_age():
+    """Test ggaDecode where differential GPS data age is provided."""
+    # Added '1.5' for age field
+    sentence = "$GPGGA,152009.00,3652.48059177,N,07620.02018248,W,1,11,0.8,3.669,M,-34.579,M,1.5,0000*57"
+    result = ggaDecode(sentence)
+    assert result["age"] == 1.5
+    assert result["diff_ref_station"] == "0000*57"
+
+
+def test_gga_decode_validate():
+    """Test ggaDecode with validation enabled."""
+    valid_sentence = "$GPGGA,152009.00,3652.48059177,N,07620.02018248,W,1,11,0.8,3.669,M,-34.579,M,,*57"
+    # Should not raise exception
+    ggaDecode(valid_sentence, validate=True)
+
+    # Invalid length (too short)
+    with pytest.raises(AssertionError):
+        ggaDecode("$GPGGA,152009", validate=True)
+
+    # Invalid length (too long)
+    too_long = "$GPGGA,152009.00,3652.48059177,N,07620.02018248,W,1,11,0.8,3.669,M,-34.579,M,1.5,00000*575757"
+    with pytest.raises(AssertionError):
+        ggaDecode(too_long, validate=True)
+
+    # Incorrect starting character
+    with pytest.raises(AssertionError):
+        ggaDecode(
+            "GPGGA,152009.00,3652.48059177,N,07620.02018248,W,1,11,0.8,3.669,M,-34.579,M,,*57",
+            validate=True,
+        )
+
+    # Incorrect sentence type
+    with pytest.raises(AssertionError):
+        ggaDecode(
+            "$GPZDA,152009.00,3652.48059177,N,07620.02018248,W,1,11,0.8,3.669,M,-34.579,M,,*57",
+            validate=True,
+        )