diff --git a/.github/workflows/docs.yml b/.github/workflows/docs.yml
index e813b80..79cb494 100644
--- a/.github/workflows/docs.yml
+++ b/.github/workflows/docs.yml
@@ -13,7 +13,7 @@ jobs:
 
       - uses: actions/setup-python@v5
         with:
-          python-version: "3.x"
+          python-version-file: pyproject.toml
           cache: "pip"
           cache-dependency-path: pyproject.toml
 
diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index e28c5f0..f484a39 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -14,7 +14,7 @@ jobs:
 
       - uses: actions/setup-python@v5
         with:
-          python-version: "3.8"
+          python-version-file: pyproject.toml
           cache: "pip"
           cache-dependency-path: pyproject.toml
 
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 4409172..ab23c37 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -21,7 +21,7 @@ jobs:
 
     - uses: actions/setup-python@v5
       with:
-        python-version: ">= 3.8"
+        python-version-file: pyproject.toml
         cache: "pip"
         cache-dependency-path: pyproject.toml
 
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index d267175..87b9046 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -11,10 +11,9 @@ jobs:
     strategy:
       matrix:
         python:
-          - "3.8"
-          - "3.9"
           - "3.10"
           - "3.11"
+          - "3.12"
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
diff --git a/src/rfc8785/__init__.py b/src/rfc8785/__init__.py
index bf1e46b..3783a39 100644
--- a/src/rfc8785/__init__.py
+++ b/src/rfc8785/__init__.py
@@ -4,11 +4,12 @@
 
 __version__ = "0.0.1"
 
-from ._impl import CanonicalizationError, IntegerDomainError, dump, dumps
+from ._impl import CanonicalizationError, FloatDomainError, IntegerDomainError, dump, dumps
 
 __all__ = [
     "CanonicalizationError",
     "IntegerDomainError",
+    "FloatDomainError",
     "dump",
     "dumps",
 ]
diff --git a/src/rfc8785/_impl.py b/src/rfc8785/_impl.py
index 32cbd4c..0a99791 100644
--- a/src/rfc8785/_impl.py
+++ b/src/rfc8785/_impl.py
@@ -49,6 +49,9 @@ class IntegerDomainError(CanonicalizationError):
     """
 
     def __init__(self, n: int) -> None:
+        """
+        Initialize an `IntegerDomainError`.
+        """
         super().__init__(f"{n} exceeds safe integer domain for JSON floats")
 
 
@@ -59,6 +62,10 @@ class FloatDomainError(CanonicalizationError):
     """
 
     def __init__(self, f: float) -> None:
+        """
+        Initialize an `FloatDomainError`.
+        """
+
         super().__init__(f"{f} is not representable in JCS")
 
 
diff --git a/test/test_impl.py b/test/test_impl.py
index e74b522..2e93323 100644
--- a/test/test_impl.py
+++ b/test/test_impl.py
@@ -72,3 +72,26 @@ def test_es6_float_stringification_full(es6_test_file):
 
             actual = sink.getvalue().decode()
             assert actual == expected
+
+
+def test_integer_domain():
+    impl.dumps(impl._INT_MAX)
+    with pytest.raises(impl.IntegerDomainError):
+        impl.dumps(impl._INT_MAX + 1)
+
+    impl.dumps(impl._INT_MIN)
+    with pytest.raises(impl.IntegerDomainError):
+        impl.dumps(impl._INT_MIN - 1)
+
+
+def test_string_invalid_utf8():
+    # escaped surrogate is fine
+    impl.dumps("\\udead")
+    with pytest.raises(impl.CanonicalizationError):
+        impl.dumps("\udead")
+
+
+def test_dumps_invalid_type():
+    with pytest.raises(impl.CanonicalizationError):
+        # set is not serializable
+        impl.dumps({1, 2, 3})
diff --git a/test/test_init.py b/test/test_init.py
index 1e391d9..44ebb63 100644
--- a/test/test_init.py
+++ b/test/test_init.py
@@ -24,3 +24,11 @@ def test_roundtrip(vector, name):
 
     actual_deserialized = json.loads(actual_output)
     assert actual_deserialized == py_input
+
+
+def test_exception_hierarchy():
+    assert issubclass(rfc8785.CanonicalizationError, ValueError)
+    assert issubclass(rfc8785.IntegerDomainError, rfc8785.CanonicalizationError)
+    assert issubclass(rfc8785.FloatDomainError, rfc8785.CanonicalizationError)
+    assert not issubclass(rfc8785.IntegerDomainError, rfc8785.FloatDomainError)
+    assert not issubclass(rfc8785.FloatDomainError, rfc8785.IntegerDomainError)