A simpler way to debug JUnit test methods.

[lobophf]

I did the following experiment. I downloaded a project from Spring Initializr that uses Gradle as a build tool. At this point, I could successfully debug a test method (with @Test annotation) by setting a breakpoint and running the :lua require'jdtls'.test_nearest_method() command. It worked as I expected.

However, without SpringBoot support, I can't do the same because the :lua require'jdtls'.test_nearest_method() command ignores the breakpoints. But, I found another way by remotely connecting the debugger to the Gradle (see the gif bellow).

My question is: There is another way to do the same process? I think my approach requires a lot of work to debug JUnit methods.

Here is my ~/.config/nvim/ftplugin/java.lua file

local HOME_PATH = os.getenv('HOME')
local ECLIPSE_JDT_LS_JAR_PATH =  HOME_PATH .. '/.config/nvim/servers/eclipse.jdt.ls/org.eclipse.jdt.ls.product/target/repository/plugins/org.eclipse.equinox.launcher_1.6.400.v20210924-0641.jar'
local ECLIPSE_JDT_LS_JAR_CONFIG_PATH = HOME_PATH .. '/.config/nvim/servers/eclipse.jdt.ls/org.eclipse.jdt.ls.product/target/repository/config_linux'
local GOOGLE_STYLE_FORMAT_XML_PATH = HOME_PATH .. '/.config/nvim/formats/google-style.xml'
local GOOGLE_STYLE_FORMAT_JAR_PATH = HOME_PATH .. '/.config/nvim/formats/google-java-format-1.15.0-all-deps.jar'
local WORKSPACE_DIR = vim.fn.fnamemodify(vim.fn.getcwd(), ':p:h:t')

local bundles = { }

-- Debugging
vim.list_extend(bundles, vim.split(vim.fn.glob( HOME_PATH .. '/.config/nvim/servers/java-debug/com.microsoft.java.debug.plugin/target/com.microsoft.java.debug.plugin*.jar' ), "\n"))
vim.list_extend(bundles, vim.split(vim.fn.glob( HOME_PATH .. '/.config/nvim/servers/vscode-java-test/server/*.jar' ), "\n"))
--vim.list_extend(bundles, vim.split(vim.fn.glob( HOME_PATH .. '/.config/nvim/servers/vscode-java-test/java-extension/com.microsoft.java.test.plugin/target/*.jar'), "\n"))

---- Decompiling
--vim.list_extend(bundles, vim.split(vim.fn.glob( HOME_PATH .. '/.config/nvim/servers/vscode-java-decompiler/server/*.jar'), "\n"))
--
--
--
local util = require('jdtls.util')
local dap = require("dap")
--require('jdtls').setup_dap({ hotcodereplace = 'auto' })
 
dap.adapters.java = function(callback)
  util.execute_command({ command = 'vscode.java.startDebugSession' }, function(err0, port)
  assert(not err0, vim.inspect(err0))
  callback({
    type = 'server',
    host = '127.0.0.1',
    port = port,
  })
  end)
end

function setKeymaps()
  local keymap = vim.api.nvim_set_keymap
  keymap('n', 'gp',':e#<CR>',{})
  keymap('n', 'gt', '<cmd>lua vim.lsp.buf.declaration()<CR>', {})
  keymap('n', 'gd', '<cmd>lua vim.lsp.buf.definition()<CR>', {})
  keymap('n', 'K', '<cmd>lua vim.lsp.buf.hover()<CR>', {})
  keymap('n', 'gi', '<cmd>lua vim.lsp.buf.implementation()<CR>', {})
  keymap('n', '<C-k>', '<cmd>lua vim.lsp.buf.signature_help()<CR>', {})
  keymap('n', '<leader>wa', '<cmd>lua vim.lsp.buf.add_workspace_folder()<CR>', {})
  keymap('n', '<leader>wr', '<cmd>lua vim.lsp.buf.remove_workspace_folder()<CR>', {})
  keymap('n', '<leader>wl', '<cmd>lua print(vim.inspect(vim.lsp.buf.list_workspace_folders()))<CR>', {})
  keymap('n', '<leader>rn', '<cmd>lua vim.lsp.buf.rename()<CR>', {})
  keymap('n', '<leader>ca', '<cmd>lua vim.lsp.buf.code_action()<CR>', {})
  keymap('n', 'gr', '<cmd>lua vim.lsp.buf.references()<CR>', {})
  keymap('n', '<leader>f', '<cmd>lua vim.lsp.buf.format({async=true})<CR>', {})
  keymap('n', '<leader>e', '<cmd>:Lex 30<CR>', {})
  keymap('n', '<leader>o', '<cmd>:lua vim.diagnostic.open_float()<CR>', {})
end

local config = {
  cmd = {
    'java',
    '-Declipse.application=org.eclipse.jdt.ls.core.id1',
    '-Dosgi.bundles.defaultStartLevel=4',
    '-Declipse.product=org.eclipse.jdt.ls.core.product',
    '-Dlog.protocol=true',
    '-Dlog.level=ALL',
    '-Xms1g',
    '--add-modules=ALL-SYSTEM',
    '--add-opens', 'java.base/java.util=ALL-UNNAMED',
    '--add-opens', 'java.base/java.lang=ALL-UNNAMED',
    '-jar', ECLIPSE_JDT_LS_JAR_PATH, GOOGLE_STYLE_FORMAT_JAR_PATH,
    '-configuration', ECLIPSE_JDT_LS_JAR_CONFIG_PATH,
    '-data', vim.fn.expand('~/.cache/nvim/workspaces_jdtls/') .. WORKSPACE_DIR 
  },
  root_dir = require('jdtls.setup').find_root({'.git', 'mvnw', 'gradlew'}),
  init_options = {
    bundles = bundles,
  },
  settings = {
    java = {
      eclipse = {
        downloadSources = true,
      },
      configuration = {
        updateBuildConfiguration = "interactive",
        runtimes = {
--          {
--             name = "JavaSE-11",
--             path = "/usr/lib/jvm/java-11-openjdk-amd64/"
--          },
          {
             name = "JavaSE-17",
             path = "/usr/lib/jvm/java-17-openjdk-amd64/"
          },
        }
      }
    },
    maven = {
      downloadSources = true,
    },
    implementationsCodeLens = {
      enabled = true,
    },
    referencesCodeLens = {
      enabled = true,
    },
    references = {
      includeDecompiledSources = true,
    },
    format = {
      enabled = true,
      settings = {
        url = GOOGLE_STYLE_FORMAT_XML_PATH,
        profile = "GoogleStyle",
      },
    },
  },
  signatureHelp = { 
    enabled = true
  },
  completion = {
    favoriteStaticMembers = {
      "org.hamcrest.MatcherAssert.assertThat",
      "org.hamcrest.Matchers.*",
      "org.hamcrest.CoreMatchers.*",
      "org.junit.jupiter.api.Assertions.*",
      "java.util.Objects.requireNonNull",
      "java.util.Objects.requireNonNullElse",
      "org.mockito.Mockito.*",
    },
    importOrder = {
      "java",
      "javax",
      "com",
      "org"
    },
  },
  sources = {
    organizeImports = {
      starThreshold = 9999,
      staticStarThreshold = 9999,
    },
  },
  codeGeneration = {
    toString = {
      template = "${object.className}{${member.name()}=${member.value}, ${otherMembers}}",
    },
    useBlocks = true,
  },
  flags = {
    allow_incremental_sync = true,
  },
  on_attach = function(client, bufnr) 
--    require('jdtls').setup_dap({ hotcodereplace = 'auto' })
    require('jdtls.dap').setup_dap_main_class_configs()
  end
}

function attach_to_debug()
  local dap = require('dap')
  dap.configurations.java = {
    {
      type = 'java';
      request = 'attach';
      name = "Attach to the process";
      hostName = 'localhost';
      port = '5005';
    },
  }
  dap.continue()
end 

setKeymaps()
require('jdtls').start_or_attach(config)

The function attach_to_debug() command is defined as follows:

function attach_to_debug()
  local dap = require('dap')
  dap.configurations.java = {
    {
      type = 'java';
      request = 'attach';
      name = "Attach to the process";
      hostName = 'localhost';
      port = '5005';
    },
  }
  dap.continue()
end 

Here is the project to test.

[mfussenegger]

Looks like there's an issue with the junit5 dependencies in your project. If you use test_nearest_method you should see an error like this in the terminal:

java.lang.NoClassDefFoundError: org/junit/platform/engine/EngineDiscoveryListener
        at java.base/java.lang.ClassLoader.defineClass1(Native Method)
        at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1012)
        at java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:150)
        at java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(BuiltinClassLoader.java:862)
        at java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(BuiltinClassLoader.java:760)
        at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:681)
        at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:639)
        at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188)
        at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:520)
        at org.junit.platform.launcher.core.ListenerRegistry.forLauncherDiscoveryListeners(ListenerRegistry.java:37)
        at org.junit.platform.launcher.core.DefaultLauncher.<init>(DefaultLauncher.java:40)
        at org.junit.platform.launcher.core.LauncherFactory.createDefaultLauncher(LauncherFactory.java:134)
        at org.junit.platform.launcher.core.LauncherFactory.create(LauncherFactory.java:125)
        at org.junit.platform.launcher.core.LauncherFactory.create(LauncherFactory.java:109)
        at org.eclipse.jdt.internal.junit5.runner.JUnit5TestLoader.<init>(JUnit5TestLoader.java:37)
        at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:77)
        at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
        at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:499)
        at java.base/java.lang.reflect.ReflectAccess.newInstance(ReflectAccess.java:128)
        at java.base/jdk.internal.reflect.ReflectionFactory.newInstance(ReflectionFactory.java:347)
        at java.base/java.lang.Class.newInstance(Class.java:645)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.createRawTestLoader(RemoteTestRunner.java:371)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.createLoader(RemoteTestRunner.java:366)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.defaultInit(RemoteTestRunner.java:310)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.init(RemoteTestRunner.java:225)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:209)
Caused by: java.lang.ClassNotFoundException: org.junit.platform.engine.EngineDiscoveryListener
        at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:641)
        at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188)
        at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:520)
        ... 27 more

Your dependencies only include the junit-jupiter-api. If you change the dependencies to the following it should work.

dependencies {
  testImplementation 'org.junit.jupiter:junit-jupiter:5.8.2'
}

[lobophf]

Thanks! Your solution works, but I'll share some details because it can be helpful for someone else.
I didn't see any stack trace, and I can run the test without issues.
But, I noticed if I change the version of junit-jupiter-api and junit-jupiter-engine to 5.8.2, as you suggested, it works.
The :lua require'jdtls'.test_nearest_method() command can hit breakpoints now. At least for this JUnit version.