Add Dan's tests

Author: stefanv

.gitignore

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+*~
+**/__pycache__

Makefile

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+test:
+	PYTHONPATH=. pytest

tests/test_lazy_loader.py

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+import sys
+import importlib
+import types
+import pytest
+
+import lazy_loader as lazy
+
+
+def test_lazy_import_basics():
+    math = lazy.load("math")
+    anything_not_real = lazy.load("anything_not_real")
+
+    # Now test that accessing attributes does what it should
+    assert math.sin(math.pi) == pytest.approx(0, 1e-6)
+    # poor-mans pytest.raises for testing errors on attribute access
+    try:
+        anything_not_real.pi
+        assert False  # Should not get here
+    except ModuleNotFoundError:
+        pass
+    assert isinstance(anything_not_real, lazy.DelayedImportErrorModule)
+    # see if it changes for second access
+    try:
+        anything_not_real.pi
+        assert False  # Should not get here
+    except ModuleNotFoundError:
+        pass
+
+
+def test_lazy_import_impact_on_sys_modules():
+    math = lazy.load("math")
+    anything_not_real = lazy.load("anything_not_real")
+
+    assert type(math) == types.ModuleType
+    assert "math" in sys.modules
+    assert type(anything_not_real) == lazy.DelayedImportErrorModule
+    assert "anything_not_real" not in sys.modules
+
+    # only do this if numpy is installed
+    np_test = pytest.importorskip("numpy")
+    np = lazy.load("numpy")
+    assert type(np) == types.ModuleType
+    assert "numpy" in sys.modules
+
+    np.pi  # trigger load of numpy
+
+    assert type(np) == types.ModuleType
+    assert "numpy" in sys.modules
+
+
+def test_lazy_import_nonbuiltins():
+    sp = lazy.load("scipy")
+    np = lazy.load("numpy")
+    if isinstance(sp, lazy.DelayedImportErrorModule):
+        try:
+            sp.pi
+            assert False
+        except ModuleNotFoundError:
+            pass
+    elif isinstance(np, lazy.DelayedImportErrorModule):
+        try:
+            np.sin(np.pi)
+            assert False
+        except ModuleNotFoundError:
+            pass
+    else:
+        assert np.sin(sp.pi) == pytest.approx(0, 1e-6)
+
+
+def test_lazy_attach():
+    name = "mymod"
+    submods = ["mysubmodule", "anothersubmodule"]
+    myall = {"not_real_submod": ["some_var_or_func"]}
+
+    locls = {
+        "attach": lazy.attach,
+        "name": name,
+        "submods": submods,
+        "myall": myall,
+    }
+    s = "__getattr__, __lazy_dir__, __all__ = attach(name, submods, myall)"
+
+    exec(s, {}, locls)
+    expected = {
+        "attach": lazy.attach,
+        "name": name,
+        "submods": submods,
+        "myall": myall,
+        "__getattr__": None,
+        "__lazy_dir__": None,
+        "__all__": None,
+    }
+    assert locls.keys() == expected.keys()
+    for k, v in expected.items():
+        if v is not None:
+            assert locls[k] == v