coveralls: 
[![Coverage Status](https://coveralls.io/builds/18988873/badge)](https://coveralls.io/builds/18988873)

Coverage increased (+0.04%) to 44.354% when pulling **7fda6f4500aa23fad0d89a64ddbdb36510c23bee on state-equiv** into **50127bd1c4e3bbdc577c7e2aaf300980e8241b0c on master**.

diff --git a/houston/state.py b/houston/state.py
index 5fdefb2..18b1fce 100644
--- a/houston/state.py
+++ b/houston/state.py
@@ -211,12 +211,20 @@ class State(object, metaclass=StateMeta):
     def time_offset(self) -> float:
         return self.__time_offset
 
-    def __eq__(self, other: 'State') -> bool:
+    def equiv(self, other: 'State') -> bool:
         if type(self) != type(other):
             msg = "illegal comparison of states: [{}] vs. [{}]"
             msg = msg.format(self.__class__.__name__, state.__class__.__name__)
             raise Exception(msg)  # FIXME use HoustonException
-        return self.__dict__ == other.__dict__
+        for v in self.__class__.variables:
+            if self.__dict__[v._field] != other.__dict__[v._field]:
+                return False
+        return True
+
+    def exact(self, other: 'State') -> bool:
+        return self.equiv(other) and self.time_offset == other.time_offset
+
+    __eq__ = exact
 
     def __getitem__(self, name: str) -> Any:
         # FIXME use frozendict

Implement State.equivalent or alter semantics of equality
Implement `State.equiv` and `State.exact`.
diff --git a/test/test_state.py b/test/test_state.py
index 0711712..007f014 100644
--- a/test/test_state.py
+++ b/test/test_state.py
@@ -66,6 +66,16 @@ def test_eq():
         assert S(foo=1, bar=2, time_offset=0.0) == Y(foo=1, bar=2, time_offset=0.0)
 
 
+def test_equiv():
+    class S(State):
+        foo = var(int, lambda c: 0)
+        bar = var(int, lambda c: 0)
+
+    assert S(foo=1, bar=1, time_offset=0.0).equiv(S(foo=1, bar=1, time_offset=0.0))
+    assert S(foo=1, bar=1, time_offset=0.0).equiv(S(foo=1, bar=1, time_offset=1.0))
+    assert not S(foo=0, bar=1, time_offset=0.0).equiv(S(foo=1, bar=1, time_offset=0.0))
+
+
 def test_to_and_from_json():
     class S(State):
         foo = var(int, lambda c: 0)

pip install -e .
parse_log_pytest
pytest
pytest
3.6
pytest --no-header -rA --tb=line --color=no -p no:cacheprovider -W ignore::DeprecationWarning
attrs==19.3.0
bugzoo==2.1.33
cement==3.0.8
certifi==2021.5.30
chardet==5.0.0
charset-normalizer==2.0.12
click==8.0.4
dataclasses==0.8
Deprecated==1.2.18
docker==5.0.3
dockerpty==0.4.1
dronekit==2.9.2
Flask==2.0.3
future==1.0.0
geographiclib==1.52
geopy==2.2.0
gitdb==4.0.9
GitPython==3.1.18
-e git+https://github.com/squaresLab/Houston.git@50127bd1c4e3bbdc577c7e2aaf300980e8241b0c#egg=houston
idna==3.10
importlib-metadata @ file:///tmp/build/80754af9/importlib-metadata_1631916693255/work
iniconfig @ file:///home/linux1/recipes/ci/iniconfig_1610983019677/work
itsdangerous==2.0.1
Jinja2==3.0.3
lxml==5.3.1
MarkupSafe==2.0.1
monotonic==1.6
more-itertools @ file:///tmp/build/80754af9/more-itertools_1637733554872/work
mypy-extensions==1.0.0
packaging @ file:///tmp/build/80754af9/packaging_1637314298585/work
pexpect==4.9.0
pluggy @ file:///tmp/build/80754af9/pluggy_1615976315926/work
psutil==7.0.0
ptyprocess==0.7.0
py @ file:///opt/conda/conda-bld/py_1644396412707/work
pymavlink==2.4.43
pyparsing @ file:///tmp/build/80754af9/pyparsing_1635766073266/work
pytest==6.2.4
PyYAML==6.0.1
requests==2.27.1
six==1.17.0
smmap==5.0.0
tabulate==0.8.10
toml @ file:///tmp/build/80754af9/toml_1616166611790/work
typing_extensions @ file:///opt/conda/conda-bld/typing_extensions_1647553014482/work
urllib3==1.26.20
websocket-client==1.3.1
Werkzeug==2.0.3
wrapt==1.16.0
zipp @ file:///tmp/build/80754af9/zipp_1633618647012/work

name: Houston
channels:
  - defaults
  - https://repo.anaconda.com/pkgs/main
  - https://repo.anaconda.com/pkgs/r
  - conda-forge
dependencies:
  - _libgcc_mutex=0.1=main
  - _openmp_mutex=5.1=1_gnu
  - ca-certificates=2025.2.25=h06a4308_0
  - certifi=2021.5.30=py36h06a4308_0
  - importlib-metadata=4.8.1=py36h06a4308_0
  - importlib_metadata=4.8.1=hd3eb1b0_0
  - iniconfig=1.1.1=pyhd3eb1b0_0
  - ld_impl_linux-64=2.40=h12ee557_0
  - libffi=3.3=he6710b0_2
  - libgcc-ng=11.2.0=h1234567_1
  - libgomp=11.2.0=h1234567_1
  - libstdcxx-ng=11.2.0=h1234567_1
  - more-itertools=8.12.0=pyhd3eb1b0_0
  - ncurses=6.4=h6a678d5_0
  - openssl=1.1.1w=h7f8727e_0
  - packaging=21.3=pyhd3eb1b0_0
  - pip=21.2.2=py36h06a4308_0
  - pluggy=0.13.1=py36h06a4308_0
  - py=1.11.0=pyhd3eb1b0_0
  - pyparsing=3.0.4=pyhd3eb1b0_0
  - pytest=6.2.4=py36h06a4308_2
  - python=3.6.13=h12debd9_1
  - readline=8.2=h5eee18b_0
  - setuptools=58.0.4=py36h06a4308_0
  - sqlite=3.45.3=h5eee18b_0
  - tk=8.6.14=h39e8969_0
  - toml=0.10.2=pyhd3eb1b0_0
  - typing_extensions=4.1.1=pyh06a4308_0
  - wheel=0.37.1=pyhd3eb1b0_0
  - xz=5.6.4=h5eee18b_1
  - zipp=3.6.0=pyhd3eb1b0_0
  - zlib=1.2.13=h5eee18b_1
  - pip:
      - attrs==19.3.0
      - bugzoo==2.1.33
      - cement==3.0.8
      - chardet==5.0.0
      - charset-normalizer==2.0.12
      - click==8.0.4
      - dataclasses==0.8
      - deprecated==1.2.18
      - docker==5.0.3
      - dockerpty==0.4.1
      - dronekit==2.9.2
      - flask==2.0.3
      - future==1.0.0
      - geographiclib==1.52
      - geopy==2.2.0
      - gitdb==4.0.9
      - gitpython==3.1.18
      - idna==3.10
      - itsdangerous==2.0.1
      - jinja2==3.0.3
      - lxml==5.3.1
      - markupsafe==2.0.1
      - monotonic==1.6
      - mypy-extensions==1.0.0
      - pexpect==4.9.0
      - psutil==7.0.0
      - ptyprocess==0.7.0
      - pymavlink==2.4.43
      - pyyaml==6.0.1
      - requests==2.27.1
      - six==1.17.0
      - smmap==5.0.0
      - tabulate==0.8.10
      - urllib3==1.26.20
      - websocket-client==1.3.1
      - werkzeug==2.0.3
      - wrapt==1.16.0
prefix: /opt/conda/envs/Houston

test/test_state.py::test_equiv
test/test_state.py::test_constructor test/test_state.py::test_is_frozen test/test_state.py::test_eq
test/test_state.py::test_variable_construction test/test_state.py::test_to_and_from_json
houston/state.py
houston/state.py