Default JAVA_HOME env in test layer to empty string

This commit changes the default value for `JAVA_HOME` in the
`CrateLayer` from `None` to `''` (empty string). This is necessary,
because environment variables are always interpreted as strings, and
therefore `None` would be interpreted as a string `'None'`, which is not
a valid path for `JAVA_HOME`.

Author: chaudum

CHANGES.txt

@@ -5,6 +5,9 @@ Changes for crate
 Unreleased
 ==========
 
+- Fixed a bug in the ``CrateLayer`` which caused ``CrateDB`` not to start up,
+  in case the ``JAVA_HOME`` environment variable was not set.
+
 2019/08/01 0.23.1
 =================
 

src/crate/testing/doctests/layer.txt

@@ -134,7 +134,7 @@ Verbosity
 
 The test layer hides the standard output of Crate per default. To increase the
 verbosity level the additional keyword argument ``verbose`` needs to be set
-to ``True``.
+to ``True``::
 
     >>> layer =  CrateLayer('crate',
     ...                     crate_home=crate_path(),
@@ -150,7 +150,7 @@ Environment variables
 ---------------------
 
 It is possible to provide  enviromental variables for the ``Crate`` testing
-layer. 
+layer::
 
     >>> layer =  CrateLayer('crate',
     ...                     crate_home=crate_path(),

src/crate/testing/layer.py

@@ -222,7 +222,7 @@ def __init__(self,
         self.verbose = verbose
         self.env = env or {}
         self.env.setdefault('CRATE_USE_IPV4', 'true')
-        self.env.setdefault('JAVA_HOME', os.environ.get('JAVA_HOME'))
+        self.env.setdefault('JAVA_HOME', os.environ.get('JAVA_HOME', ''))
         self._stdout_consumers = []
         self.conn_pool = urllib3.PoolManager(num_pools=1)
 

src/crate/testing/test_layer.py

@@ -19,9 +19,11 @@
 # with Crate these terms will supersede the license and you may use the
 # software solely pursuant to the terms of the relevant commercial agreement.
 
-from unittest import TestCase
+import os
+import tempfile
+from unittest import TestCase, mock
 from io import BytesIO
-from .layer import prepend_http, http_url_from_host_port, wait_for_http_url
+from .layer import CrateLayer, prepend_http, http_url_from_host_port, wait_for_http_url
 
 
 class LayerUtilsTest(TestCase):
@@ -55,3 +57,28 @@ def test_wait_for_http(self):
         log = BytesIO(b'[i.c.p.h.CrateNettyHttpServerTransport] [crate] publish_address {}')
         addr = wait_for_http_url(log=log, timeout=1)
         self.assertEqual(None, addr)
+
+    @mock.patch.dict('os.environ', {}, clear=True)
+    def test_java_home_env_not_set(self):
+        with tempfile.TemporaryDirectory() as tmpdir:
+            layer = CrateLayer('java-home-test', tmpdir)
+            # JAVA_HOME must not be set to `None`, since it would be interpreted as a
+            # string 'None', and therefore intepreted as a path
+            self.assertEqual(layer.env['JAVA_HOME'], '')
+
+    @mock.patch.dict('os.environ', {}, clear=True)
+    def test_java_home_env_set(self):
+        java_home = '/usr/lib/jvm/java-11-openjdk-amd64'
+        with tempfile.TemporaryDirectory() as tmpdir:
+            os.environ['JAVA_HOME'] = java_home
+            layer = CrateLayer('java-home-test', tmpdir)
+            self.assertEqual(layer.env['JAVA_HOME'], java_home)
+
+    @mock.patch.dict('os.environ', {}, clear=True)
+    def test_java_home_env_override(self):
+        java_11_home = '/usr/lib/jvm/java-11-openjdk-amd64'
+        java_12_home = '/usr/lib/jvm/java-12-openjdk-amd64'
+        with tempfile.TemporaryDirectory() as tmpdir:
+            os.environ['JAVA_HOME'] = java_11_home
+            layer = CrateLayer('java-home-test', tmpdir, env={'JAVA_HOME': java_12_home})
+            self.assertEqual(layer.env['JAVA_HOME'], java_12_home)