Add fixture for base directory of saving plots.

- Use this fixture in TestW7, by creating per-setup
  subdirectories (currently only W7, would be enhanced
  by parametrization later).

- Directories are named as per git commit hashes.

tardis/tests/tests_slow/conftest.py

@@ -2,6 +2,7 @@
 import numpy as np
 import pytest
 from astropy import units as u
+import tardis
 
 
 @pytest.fixture(scope="session")
@@ -18,6 +19,19 @@ def data_path():
     return os.path.join(os.path.dirname(os.path.realpath(__file__)), "w7")
 
 
+@pytest.fixture(scope="session")
+def base_plot_dir():
+    githash_short = tardis.__githash__[0:7]
+    base_plot_dir = os.path.join("/tmp", "plots", githash_short)
+
+    # Remove plots generated from previous runs on same githash.
+    if os.path.exists(base_plot_dir):
+        os.rmdir(base_plot_dir)
+
+    os.makedirs(base_plot_dir)
+    return base_plot_dir
+
+
 @pytest.fixture(scope="session")
 def reference(request, slow_tests_datadir):
     """

tardis/tests/tests_slow/test_w7.py

@@ -20,7 +20,7 @@ class TestW7(object):
     @classmethod
     @pytest.fixture(scope="class", autouse=True)
     def setup(self, request, reference, data_path, atomic_data_fname,
-              slow_tests_datadir):
+              slow_tests_datadir, base_plot_dir):
         """
         This method does initial setup of creating configuration and performing
         a single run of integration test.
@@ -58,6 +58,12 @@ def setup(self, request, reference, data_path, atomic_data_fname,
         # Get the reference data through the fixture.
         self.reference = reference
 
+        # Form a base directory to save plots for `W7` setup.
+        # TODO: Rough prototyping, parametrize this as more setups are added.
+        self.name = "w7"
+        self.base_plot_dir = os.path.join(base_plot_dir, self.name)
+        os.makedirs(self.base_plot_dir)
+
     def test_j_estimators(self):
         assert_allclose(
                 self.reference['j_estimators'],
@@ -152,7 +158,7 @@ def plot_spectrum(self, passed):
 
         # Figure is saved in `tmp` directory right now, till a suitable way of
         # saving them is decided.
-        plt.savefig(os.path.join(self.plot_savedir, "spectrum.png"))
+        plt.savefig(os.path.join(self.base_plot_dir, "spectrum.png"))
 
     def test_montecarlo_properties(self):
         assert_quantity_allclose(