Add behaviour tests for showing and saving datasets

Three scenarios were added, testing showing a dataset, saving a dataset,
and bulk saving datasets (`save_datasets`).

Signed-off-by: Martin Raspaud <martin.raspaud@smhi.se>

mpop/tests/features/feature-save.feature

@@ -0,0 +1,24 @@
+# Created by a001673 at 2015-12-07
+Feature: Simple and intuitive saving
+
+  Visualization of the data is important and should be an easy one-line, like eg
+  show(my_dataset). In a similar way, saving the data to disk should be simple,
+  for example save(dataset, filename), with sensible defaults provided depending
+  on the filename extension (eg. geotiff for .tif, netcdf for .nc). Saving
+  several datasets at once would be nice to have.
+
+  Scenario: 1-step showing dataset
+    Given a dataset is available
+    When the show command is called
+    Then an image should pop up
+
+  Scenario: 1-step saving dataset
+    Given a dataset is available
+    When the save_dataset command is called
+    Then a file should be saved on disk
+
+  Scenario: 1-step saving all datasets
+    Given a bunch of datasets are available
+    When the save_datasets command is called
+    Then a bunch of files should be saved on disk
+

mpop/tests/features/steps/steps-save.py

@@ -0,0 +1,93 @@
+from behave import *
+from mock import patch
+
+use_step_matcher("re")
+
+
+@given("a dataset is available")
+def step_impl(context):
+    """
+    :type context: behave.runner.Context
+    """
+    from mpop.scene import Scene
+    from datetime import datetime
+    from mpop.projectable import Projectable
+    scn = Scene(platform_name="Suomi-NPP", sensor="viirs",
+                start_time=datetime(2015, 3, 11, 11, 20),
+                end_time=datetime(2015, 3, 11, 11, 26))
+    scn["MyDataset"] = Projectable([[1, 2], [3, 4]])
+    context.scene = scn
+
+
+@when("the show command is called")
+def step_impl(context):
+    """
+    :type context: behave.runner.Context
+    """
+    with patch('trollimage.image.Image.show') as mock_show:
+        context.scene.show("MyDataset")
+        mock_show.assert_called_once_with()
+
+
+@then("an image should pop up")
+def step_impl(context):
+    """
+    :type context: behave.runner.Context
+    """
+    pass
+
+
+@when("the save_dataset command is called")
+def step_impl(context):
+    """
+    :type context: behave.runner.Context
+    """
+    context.filename = "/tmp/test_dataset.png"
+    context.scene.save_dataset("MyDataset", context.filename)
+
+
+@then("a file should be saved on disk")
+def step_impl(context):
+    """
+    :type context: behave.runner.Context
+    """
+    import os
+    assert(os.path.exists(context.filename))
+    os.remove(context.filename)
+
+
+@given("a bunch of datasets are available")
+def step_impl(context):
+    """
+    :type context: behave.runner.Context
+    """
+    from mpop.scene import Scene
+    from datetime import datetime
+    from mpop.projectable import Projectable
+    scn = Scene(platform_name="Suomi-NPP", sensor="viirs",
+                start_time=datetime(2015, 3, 11, 11, 20),
+                end_time=datetime(2015, 3, 11, 11, 26))
+    scn["MyDataset"] = Projectable([[1, 2], [3, 4]])
+    scn["MyDataset2"] = Projectable([[5, 6], [7, 8]])
+    context.scene = scn
+
+
+
+@when("the save_datasets command is called")
+def step_impl(context):
+    """
+    :type context: behave.runner.Context
+    """
+    context.scene.save_datasets(writer="simple_image", file_pattern="{name}.png")
+
+
+
+@then("a bunch of files should be saved on disk")
+def step_impl(context):
+    """
+    :type context: behave.runner.Context
+    """
+    import os
+    for filename in ["MyDataset.png", "MyDataset2.png"]:
+        assert(os.path.exists(filename))
+        os.remove(filename)