CI: Add verification CI job

.github/workflows/ci.yml

@@ -186,6 +186,62 @@ jobs:
         with:
           name: Flaky unittest report ${{ matrix.os }}-${{ matrix.pixi-environment }}
           path: ${{ env.COVERAGE_REPORT }}
+  validation-test:
+    name: "Validation tests | pixi run tests-validation"
+    runs-on: ubuntu-latest
+    needs: [cache-pixi-lock]
+    permissions:
+      contents: read
+    env:
+      COVERAGE_REPORT: "ubuntu_test_validation_test_report.html"
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          persist-credentials: false
+      - name: Restore cached pixi lockfile
+        uses: Parcels-code/pixi-lock/restore@38495788b79a5ff26009aecc15daa9a8310b8832 # v0.1.0
+        with:
+          cache-key: ${{ needs.cache-pixi-lock.outputs.cache-key }}
+      - uses: prefix-dev/setup-pixi@fef5c9568ca6c4ff7707bf840ab0692ba3f08293 # v0.9.0
+        with:
+          pixi-version: ${{ needs.cache-pixi-lock.outputs.pixi-version }}
+          locked: false # TODO: Remove once v7 of the lock file is removed, or once we stop having external source dependencies https://github.com/Parcels-code/Parcels/pull/2550#issuecomment-4088660238
+          cache: true
+          cache-write: ${{ github.event_name == 'push' && github.ref_name == 'main' }}
+      # https://github.com/actions/cache/blob/main/tips-and-workarounds.md#update-a-cache
+      - name: Restore cached hypothesis directory
+        id: restore-hypothesis-cache
+        uses: actions/cache/restore@27d5ce7f107fe9357f9df03efb73ab90386fccae # v5.0.5
+        with:
+          path: .hypothesis/
+          key: cache-hypothesis-${{ runner.os }}-${{ github.run_id }}
+          restore-keys: |
+            cache-hypothesis-${{ runner.os }}-
+      - name: Validation test
+        id: unit-test
+        run: |
+          pixi run tests-validation -v -s --cov=parcels --cov-report=xml --html="${COVERAGE_REPORT}" --self-contained-html
+      # explicitly save the cache so it gets updated, also do this even if it fails.
+      - name: Save cached hypothesis directory
+        id: save-hypothesis-cache
+        if: always() && steps.unit-test.outcome != 'skipped'
+        uses: actions/cache/save@27d5ce7f107fe9357f9df03efb73ab90386fccae # v5.0.5
+        with:
+          path: .hypothesis/
+          key: cache-hypothesis-${{ runner.os }}-${{ github.run_id }}
+      - name: Codecov
+        uses: codecov/codecov-action@5a1091511ad55cbe89839c7260b706298ca349f7 # v5.5.1
+        env:
+          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }} # zizmor: ignore[secrets-outside-env]
+        with:
+          flags: unit-tests
+      - name: Upload test results
+        if: ${{ always() }} # Always run this step, even if tests fail
+        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
+        with:
+          name: Validation test report ubuntu-test
+          path: ${{ env.COVERAGE_REPORT }}
+
   integration-test:
     name: "Integration: ${{ matrix.os }} | pixi run -e ${{ matrix.pixi-environment }} tests-notebooks"
     runs-on: ${{ matrix.os }}-latest