From bcd28aba6976e233d5d43decdb4dc79d0b62ff5e Mon Sep 17 00:00:00 2001
From: Sean Gillies <sean.gillies@gmail.com>
Date: Thu, 3 Sep 2015 11:15:54 -0600
Subject: [PATCH] Tests added for merge tool

A follow on to #460. Would have insisted on tests in the PR, but
it's not super clear where to start for new developers. Also, the
tool was pretty well exercised by the existing CLI test. The new
tests are a straightforward port of the CLI tests.
---
 rasterio/tools/merge.py | 2 +-
 rasterio/transform.py   | 9 +++++++++
 tests/test_rio_merge.py | 1 +
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/rasterio/tools/merge.py b/rasterio/tools/merge.py
index 858ddb39..07d9c411 100644
--- a/rasterio/tools/merge.py
+++ b/rasterio/tools/merge.py
@@ -8,7 +8,7 @@ from rasterio._base import get_index, get_window
 from rasterio.transform import Affine
 
 
-def merge(sources, bounds=(), res=(), nodata=None):
+def merge(sources, bounds=None, res=None, nodata=None):
     """Copy valid pixels from input files to an output file.
 
     All files must have the same number of bands, data type, and
diff --git a/rasterio/transform.py b/rasterio/transform.py
index c02bc1cc..b8327116 100644
--- a/rasterio/transform.py
+++ b/rasterio/transform.py
@@ -2,6 +2,7 @@ import warnings
 
 from affine import Affine
 
+
 IDENTITY = Affine.identity()
 
 
@@ -38,3 +39,11 @@ def from_bounds(west, south, east, north, width, height):
     `height` in number of pixels."""
     return Affine.translation(west, north) * Affine.scale(
             (east - west)/width, (south - north)/height)
+
+
+def array_bounds(height, width, transform):
+    """Return the `west, south, east, north` bounds of an array given
+    its height, width, and an affine transform."""
+    w, n = transform.xoff, transform.yoff
+    e, s = transform * (width, height)
+    return w, s, e, n
diff --git a/tests/test_rio_merge.py b/tests/test_rio_merge.py
index d492373c..95f7bc6f 100644
--- a/tests/test_rio_merge.py
+++ b/tests/test_rio_merge.py
@@ -95,6 +95,7 @@ def test_merge_warn(test_data_dir_1):
     runner = CliRunner()
     result = runner.invoke(merge, inputs + [outputname] + ['--nodata', '-1'])
     assert result.exit_code == 0
+    assert os.path.exists(outputname)
     assert "using the --nodata option for better results" in result.output