CI: Run unit tests via gitlab CI

.ci/unit_tests.sh

+#!/usr/bin/env bash
+
+conda create                                                      \
+      -c https://fsl.fmrib.ox.ac.uk/fsldownloads/fslconda/public/ \
+      -c conda-forge                                              \
+      -p ./test.env                                               \
+      "python=${PYTHON_VERSION}"                                  \
+      pytest                                                      \
+      coverage                                                    \
+      pytest-cov
+
+source activate ./test.env
+
+pip install --no-deps -e .
+
+pytest

.gitlab-ci.yml

+stages:
+ - test
+
+
+.test: &test_template
+  stage: test
+  image: continuumio/miniconda3
+  tags:
+    - docker
+  except:
+    - tags
+    - merge_requests
+  script:
+    - bash ./.ci/unit_tests.sh
+
+
+test:3.11:
+  variables:
+    PYTHON_VERSION : "3.11"
+  <<: *test_template