Install pytest et al

Author: weiji14

.github/workflows/ci_tests.yaml

@@ -131,7 +131,7 @@ jobs:
       # Install build dependencies from conda-forge
       - name: Install build dependencies
         shell: bash -l {0}
-        run: conda install cmake libblas libcblas liblapack fftw gdal ghostscript libnetcdf hdf5 zlib curl pcre gshhg-gmt dcw-gmt
+        run: conda install cmake libblas libcblas liblapack fftw gdal ghostscript libnetcdf hdf5 zlib curl pcre gshhg-gmt dcw-gmt pytest pytest-cov pytest-mpl
 
       # Install GMT master branch
       - name: Install GMT from master