test: rfc: refactor: run_float_fn -> run_float_fn_approx (#507)

Uses `pytest.approx`, see
https://docs.pytest.org/en/stable/reference/reference.html#pytest-approx,
with optional configurable `rel` and `abs`.

tests/integration/conftest.py

@@ -97,6 +97,22 @@ def f(module: ModulePointer, expected: Any, fn_name: str = "main"):
 def run_int_fn():
     return _run_fn("run_int_function")
 
+
 @pytest.fixture
-def run_float_fn():
-    return _run_fn("run_float_function")
+def run_float_fn_approx():
+    """Like run_int_fn, but takes optional additional parameters `rel`, `abs` and `nan_ok`
+    as per `pytest.approx`."""
+    run_fn = _run_fn("run_float_function")
+
+    def run_approx(
+        hugr: Package,
+        expected: float,
+        fn_name: str = "main",
+        *,
+        rel: float | None = None,
+        abs: float | None = None,
+        nan_ok: bool = False,
+    ):
+        return run_fn(hugr, pytest.approx(expected, rel=rel, abs=abs, nan_ok=nan_ok))
+
+    return run_approx

tests/integration/test_arithmetic.py

@@ -251,7 +251,7 @@ def run_rem() -> int:
     run_int_fn(hugr, expected=2, fn_name="run_rem")
 
 
-def test_angle_exec(validate, run_float_fn):
+def test_angle_exec(validate, run_float_fn_approx):
     module = GuppyModule("test_angle_exec")
     module.load_all(angles)
 
@@ -266,4 +266,4 @@ def main() -> float:
     hugr = module.compile()
     validate(hugr)
     import math
-    run_float_fn(hugr, expected=pytest.approx(-6 * math.pi))
+    run_float_fn_approx(hugr, expected=-6 * math.pi)