tests: Add tests for Balance.copy() tolerance handling.

I wrote the changes to Balance.format() before the dependent changes to
Balance.copy(), so I was sort of counting on them to be implicitly
tested. But they should be explicit.

tests/test_reports_balance.py

@@ -345,11 +345,23 @@ def test_iadd_balance(mapping):
     expected = core.Balance(amounts_from_map(expect_numbers))
     assert balance == expected
 
-def test_copy():
-    amounts = frozenset(amounts_from_map({'USD': 10, 'EUR': '.001'}))
-    # Use a ridiculous tolerance to test it doesn't matter.
-    actual = core.Balance(amounts, 100).copy()
-    assert frozenset(actual.values()) == amounts
+@pytest.mark.parametrize('tolerance', TOLERANCES)
+def test_copy(tolerance):
+    eur = testutil.Amount('.003', 'EUR')
+    source = core.Balance([eur], tolerance)
+    new = source.copy()
+    assert source is not new
+    assert dict(source) == dict(new)
+    assert new.tolerance == tolerance
+
+@pytest.mark.parametrize('tolerance', TOLERANCES)
+def test_copy_tolerance_arg(tolerance):
+    eur = testutil.Amount('.003', 'EUR')
+    source = core.Balance([eur])
+    new = source.copy(tolerance)
+    assert source is not new
+    assert dict(source) == dict(new)
+    assert new.tolerance == tolerance
 
 @pytest.mark.parametrize('tolerance', TOLERANCES)
 def test_clean_copy(tolerance):
@@ -361,6 +373,7 @@ def test_clean_copy(tolerance):
     else:
         expected = {usd}
     assert frozenset(actual.values()) == expected
+    assert actual.tolerance == tolerance
 
 @pytest.mark.parametrize('tolerance', TOLERANCES)
 def test_clean_copy_arg(tolerance):
@@ -372,6 +385,7 @@ def test_clean_copy_arg(tolerance):
     else:
         expected = {usd}
     assert frozenset(actual.values()) == expected
+    assert actual.tolerance == tolerance
 
 @pytest.mark.parametrize('mapping,expected', DEFAULT_STRINGS)
 def test_str(mapping, expected):