Massively reduce the amount of code needed for linter tests

test/command_callback/test_php_langserver_callbacks.vader

@@ -1,49 +1,29 @@
 Before:
-  Save g:ale_php_langserver_executable
-  Save g:ale_php_langserver_config_path
-  Save g:ale_php_langserver_use_global
-
-  unlet! g:ale_php_langserver_executable
-  unlet! g:ale_php_langserver_config_path
-  unlet! g:ale_php_langserver_use_global
-
-  runtime ale_linters/php/langserver.vim
-
-  call ale#test#SetDirectory('/testplugin/test/command_callback')
+  call ale#assert#SetUpLinterTest('php', 'langserver')
 
 After:
-  Restore
-
   if isdirectory(g:dir . '/.git')
     call delete(g:dir . '/.git', 'd')
   endif
 
-  call ale#test#RestoreDirectory()
-  call ale#linter#Reset()
+  call ale#assert#TearDownLinterTest()
 
 Execute(The default executable path should be correct):
-  AssertEqual
-  \ 'php-language-server.php',
-  \ ale_linters#php#langserver#GetExecutable(bufnr(''))
-  AssertEqual
-  \ 'php ' . ale#Escape('php-language-server.php'),
-  \ ale_linters#php#langserver#GetCommand(bufnr(''))
+  AssertLinter 'php-language-server.php',
+  \ 'php ' . ale#Escape('php-language-server.php')
 
 Execute(Vendor executables should be detected):
   call ale#test#SetFilename('php-langserver-project/test.php')
 
-  AssertEqual
+  AssertLinter
   \ ale#path#Simplify(g:dir . '/php-langserver-project/vendor/bin/php-language-server.php'),
-  \ ale_linters#php#langserver#GetExecutable(bufnr(''))
-  AssertEqual
   \ 'php ' . ale#Escape(ale#path#Simplify(
   \   g:dir
   \   . '/php-langserver-project/vendor/bin/php-language-server.php'
-  \ )),
-  \ ale_linters#php#langserver#GetCommand(bufnr(''))
+  \ ))
 
 Execute(The project path should be correct for .git directories):
   call ale#test#SetFilename('php-langserver-project/test.php')
   call mkdir(g:dir . '/.git')
 
-  AssertEqual g:dir, ale_linters#php#langserver#GetProjectRoot(bufnr(''))
+  AssertLSPProject g:dir