diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
new file mode 100644
index 0000000..23cc6e7
--- /dev/null
+++ b/.github/workflows/tests.yml
@@ -0,0 +1,58 @@
+name: Tests
+
+on:
+  push:
+    branches: [master, develop]
+  pull_request:
+    branches: [master, develop]
+
+jobs:
+  test-python:
+    name: Python ${{ matrix.python-version }}
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: ["3.9", "3.10", "3.11", "3.12"]
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+
+      - name: Install package
+        run: pip install -e .
+
+      - name: Run tests
+        run: |
+          cd tests
+          python run_tests.py
+
+  test-micropython:
+    name: MicroPython (Unix port)
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+
+      - name: Install MicroPython Unix port
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y build-essential libffi-dev pkg-config
+          git clone --depth 1 https://github.com/micropython/micropython.git /tmp/micropython
+          cd /tmp/micropython/ports/unix
+          make submodules
+          make
+
+      - name: Run tests on MicroPython
+        run: |
+          cd tests
+          /tmp/micropython/ports/unix/build-standard/micropython run_tests.py
+        continue-on-error: true  # MicroPython may lack some deps
diff --git a/src/embit/networks.py b/src/embit/networks.py
index 6f1a541..dc853a4 100644
--- a/src/embit/networks.py
+++ b/src/embit/networks.py
@@ -1,5 +1,20 @@
 from .misc import const
 
+
+def get_network(name):
+    """
+    Get network by name with testnet4 fallback.
+    Bitcoin Core 28.0+ uses 'testnet4' as the network name,
+    which has the same address parameters as testnet3.
+    """
+    if name in NETWORKS:
+        return NETWORKS[name]
+    # testnet4 uses same parameters as testnet3
+    if name == "testnet4":
+        return NETWORKS["test"]
+    return None
+
+
 NETWORKS = {
     "main": {
         "name": "Mainnet",
@@ -73,4 +88,24 @@
         "Zpub": b"\x02\x57\x54\x83",
         "bip32": const(1),
     },
+    # testnet4: Bitcoin Core 28.0+ replacement for testnet3
+    # Uses identical address parameters (bech32 "tb", same xpub/xprv versions)
+    "testnet4": {
+        "name": "Testnet4",
+        "wif": b"\xEF",
+        "p2pkh": b"\x6F",
+        "p2sh": b"\xC4",
+        "bech32": "tb",
+        "xprv": b"\x04\x35\x83\x94",
+        "xpub": b"\x04\x35\x87\xcf",
+        "yprv": b"\x04\x4a\x4e\x28",
+        "zprv": b"\x04\x5f\x18\xbc",
+        "Yprv": b"\x02\x42\x85\xb5",
+        "Zprv": b"\x02\x57\x50\x48",
+        "ypub": b"\x04\x4a\x52\x62",
+        "zpub": b"\x04\x5f\x1c\xf6",
+        "Ypub": b"\x02\x42\x89\xef",
+        "Zpub": b"\x02\x57\x54\x83",
+        "bip32": const(1),
+    },
 }
diff --git a/tests/tests/test_networks.py b/tests/tests/test_networks.py
new file mode 100644
index 0000000..acc522a
--- /dev/null
+++ b/tests/tests/test_networks.py
@@ -0,0 +1,65 @@
+"""Tests for network definitions and get_network function."""
+
+from embit import networks
+from unittest import TestCase
+
+
+class TestNetworks(TestCase):
+    """Test Bitcoin network definitions."""
+
+    def test_all_networks_present(self):
+        """All expected Bitcoin networks should be defined."""
+        expected = ["main", "test", "regtest", "signet", "testnet4"]
+        for name in expected:
+            self.assertIn(name, networks.NETWORKS)
+
+    def test_testnet4_parameters(self):
+        """testnet4 should have same parameters as testnet3."""
+        test = networks.NETWORKS["test"]
+        testnet4 = networks.NETWORKS["testnet4"]
+
+        # Same address parameters
+        self.assertEqual(testnet4["bech32"], test["bech32"])
+        self.assertEqual(testnet4["bech32"], "tb")
+        self.assertEqual(testnet4["p2pkh"], test["p2pkh"])
+        self.assertEqual(testnet4["p2sh"], test["p2sh"])
+        self.assertEqual(testnet4["wif"], test["wif"])
+
+        # Same xpub/xprv versions
+        self.assertEqual(testnet4["xpub"], test["xpub"])
+        self.assertEqual(testnet4["xprv"], test["xprv"])
+        self.assertEqual(testnet4["zpub"], test["zpub"])
+        self.assertEqual(testnet4["zprv"], test["zprv"])
+
+        # Same coin type
+        self.assertEqual(testnet4["bip32"], test["bip32"])
+
+    def test_get_network_direct(self):
+        """get_network should return network by name."""
+        main = networks.get_network("main")
+        self.assertEqual(main["name"], "Mainnet")
+        self.assertEqual(main["bech32"], "bc")
+
+        test = networks.get_network("test")
+        self.assertEqual(test["name"], "Testnet")
+        self.assertEqual(test["bech32"], "tb")
+
+    def test_get_network_testnet4(self):
+        """get_network should handle testnet4."""
+        testnet4 = networks.get_network("testnet4")
+        self.assertIsNotNone(testnet4)
+        self.assertEqual(testnet4["name"], "Testnet4")
+        self.assertEqual(testnet4["bech32"], "tb")
+
+    def test_get_network_unknown(self):
+        """get_network should return None for unknown networks."""
+        result = networks.get_network("unknown_network")
+        self.assertIsNone(result)
+
+    def test_mainnet_bech32(self):
+        """Mainnet should use 'bc' prefix."""
+        self.assertEqual(networks.NETWORKS["main"]["bech32"], "bc")
+
+    def test_regtest_bech32(self):
+        """Regtest should use 'bcrt' prefix."""
+        self.assertEqual(networks.NETWORKS["regtest"]["bech32"], "bcrt")