Viewing github.com/django/django-stable-4.1.x/tests/utils_tests/test_topological_sort.py

```
from django.test import SimpleTestCase
```

from django.utils.topological_sort import (

```
    CyclicDependencyError,
```
```
    stable_topological_sort,
```
```
    topological_sort_as_sets,
```
```
)
```

class TopologicalSortTests(SimpleTestCase):

```
    def test_basic(self):
```
```
        dependency_graph = {
```
```
            1: {2, 3},
```
```
            2: set(),
```
```
            3: set(),
```
```
            4: {5, 6},
```
```
            5: set(),
```
```
            6: {5},
```
```
        }
```
```
        self.assertEqual(
```

            list(topological_sort_as_sets(dependency_graph)), [{2, 3, 5}, {1, 6}, {4}]

```
        )
```
```
        self.assertEqual(
```

            stable_topological_sort([1, 2, 3, 4, 5, 6], dependency_graph),

```
            [2, 3, 5, 1, 6, 4],
```
```
        )
```
```
    def test_cyclic_dependency(self):
```

        msg = "Cyclic dependency in graph: (1, {2}), (2, {1})"

        with self.assertRaisesMessage(CyclicDependencyError, msg):

            list(topological_sort_as_sets({1: {2}, 2: {1}}))

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