Try and run pytest in CI

.github/workflows/tests.yml

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+name: Test CI
+
+on:
+  push:
+  pull_request:
+  schedule:
+    # Run every Monday at 8am to check latest versions of dependencies
+    - cron: "0 8 * * WED"
+
+jobs:
+  tests:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      - name: Log in to the Container registry
+        uses: docker/login-action@f054a8b539a109f9f41c372932f1ae047eff08c9
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract metadata (tags, labels) for Docker
+        id: meta
+        uses: docker/metadata-action@98669ae865ea3cffbcbaa878cf57c20bbf1c6c38
+        with:
+          images: |
+            ghcr.io/${{ github.repository }}
+          tags: |
+            type=edge,branch=main
+            type=ref,event=branch
+            type=semver,pattern={{version}}
+            type=sha,prefix=
+
+      - name: Build and push Docker image
+        uses: docker/build-push-action@ad44023a93711e3deb337508980b4b5e9bcdc5dc
+        with:
+          context: .
+          push: false
+          tags: test
+          labels: ${{ steps.meta.outputs.labels }}
+
+      - name: Test
+        run: |
+          docker exec test bash -c "pytest"

tests/test_internals.py

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+from pymca_zocalo.internals import find_cut_off_energy
+import tempfile
+from pytest import raises
+from unittest.mock import patch, mock_open
+
+
+@patch("pymca_zocalo.internals.open")
+def test_GIVEN_input_file_not_found_WHEN_find_cut_off_energy_called_THEN_raises_exception(mock_open):
+    mock_open.side_effect = FileNotFoundError()
+    with raises(FileNotFoundError):
+        find_cut_off_energy("test_file_name", 0)
+
+
+@patch("pymca_zocalo.internals.open", new_callable=mock_open, read_data="1 0")
+def test_GIVEN_energy_of_1_and_cutoff_of_0_WHEN_find_cut_off_energy_called_THEN_returns_1(mock_file):
+    line_of_greater_energy = find_cut_off_energy("test_file_name", 0)
+    assert line_of_greater_energy == 0
+
+@patch("pymca_zocalo.internals.open")
+def test_different_energies(mock_file):
+    test_data = "0 1\n5 10\n"
+    mock_open(mock_file, read_data=test_data)
+    line_of_greater_energy = find_cut_off_energy("test_file_name", 2)
+    assert line_of_greater_energy == 1
+
+
+@patch("pymca_zocalo.internals.open")
+def test_file_has_non_floats_different_energies(mock_file):
+    test_data = "hyadasd 1\n5 10\n"
+    mock_open(mock_file, read_data=test_data)
+    line_of_greater_energy = find_cut_off_energy("test_file_name", 2)
+    assert line_of_greater_energy == 1
+
+@patch("pymca_zocalo.internals.open")
+def test_file_nothing_in_then_gives_none(mock_file):
+    test_data = ""
+    mock_open(mock_file, read_data=test_data)
+    line_of_greater_energy = find_cut_off_energy("test_file_name", 2)
+    assert line_of_greater_energy == None