Massively reduce the amount of code needed for linter tests

test/command_callback/test_mercury_mmc_command_callback.vader

@@ -1,42 +1,25 @@
 Before:
-  Save g:ale_mercury_mmc_executable
-  Save g:ale_mercury_mmc_options
-
-  unlet! g:ale_mercury_mmc_executable
-  unlet! b:ale_mercury_mmc_executable
-  unlet! g:ale_mercury_mmc_options
-  unlet! b:ale_mercury_mmc_options
-
-  runtime ale_linters/mercury/mmc.vim
-  call ale#test#SetDirectory('/testplugin/test/command_callback')
+  call ale#assert#SetUpLinterTest('mercury', 'mmc')
+  call ale#test#SetFilename('dummy')
 
 After:
-  unlet! b:ale_mercury_mmc_executable
-  unlet! b:ale_mercury_mmc_options
-
-  Restore
-  call ale#test#RestoreDirectory()
-  call ale#linter#Reset()
+  call ale#assert#TearDownLinterTest()
 
 Execute(The default command should be correct):
-  AssertEqual
+  AssertLinter 'mmc',
   \ ale#path#BufferCdString(bufnr(''))
-  \ . 'mmc --errorcheck-only --make --output-compile-error-lines 100 dummy',
-  \
-  \ ale_linters#mercury#mmc#GetCommand(bufnr(''))
+  \ . 'mmc --errorcheck-only --make --output-compile-error-lines 100 dummy'
 
 Execute(The executable should be configurable):
   let b:ale_mercury_mmc_executable = 'foo'
-  AssertEqual
+
+  AssertLinter 'foo',
   \ ale#path#BufferCdString(bufnr(''))
-  \ . 'foo --errorcheck-only --make --output-compile-error-lines 100 dummy',
-  \
-  \ ale_linters#mercury#mmc#GetCommand(bufnr(''))
+  \ . 'foo --errorcheck-only --make --output-compile-error-lines 100 dummy'
 
 Execute(The options should be configurable):
   let b:ale_mercury_mmc_options = '--bar'
-  AssertEqual
+
+  AssertLinter 'mmc',
   \ ale#path#BufferCdString(bufnr(''))
-  \ . 'mmc --errorcheck-only --bar dummy',
-  \
-  \ ale_linters#mercury#mmc#GetCommand(bufnr(''))
+  \ . 'mmc --errorcheck-only --bar dummy'