Add some tests for ENV.{append,prepend} behavior

Library/Homebrew/test/test_ENV.rb

@@ -57,6 +57,52 @@ class EnvironmentTests < Test::Unit::TestCase
     assert_equal expected, @env.methods
   end
 
+  def test_append_existing_key
+    @env['foo'] = 'bar'
+    @env.append 'foo', '1'
+    assert_equal 'bar 1', @env['foo']
+  end
+
+  def test_append_existing_key_empty
+    @env['foo'] = ''
+    @env.append 'foo', '1'
+    assert_equal '1', @env['foo']
+  end
+
+  def test_append_missing_key
+    @env.append 'foo', '1'
+    assert_equal '1', @env['foo']
+  end
+
+  def test_prepend_existing_key
+    @env['foo'] = 'bar'
+    @env.prepend 'foo', '1'
+    assert_equal '1 bar', @env['foo']
+  end
+
+  def test_prepend_existing_key_empty
+    @env['foo'] = ''
+    @env.prepend 'foo', '1'
+    assert_equal '1', @env['foo']
+  end
+
+  def test_prepend_missing_key
+    @env.prepend 'foo', '1'
+    assert_equal '1', @env['foo']
+  end
+
+  # NOTE: this may be a wrong behavior; we should probably reject objects that
+  # do not respond to #to_str. For now this documents existing behavior.
+  def test_append_coerces_value_to_string
+    @env.append 'foo', 42
+    assert_equal '42', @env['foo']
+  end
+
+  def test_prepend_coerces_value_to_string
+    @env.prepend 'foo', 42
+    assert_equal '42', @env['foo']
+  end
+
   def test_append_path
     @env.append_path 'FOO', '/usr/bin'
     assert_equal '/usr/bin', @env['FOO']