diff --git a/lua/neotest-golang/lib/json.lua b/lua/neotest-golang/lib/json.lua
index 2c0b909d..2fcd6e5a 100644
--- a/lua/neotest-golang/lib/json.lua
+++ b/lua/neotest-golang/lib/json.lua
@@ -6,8 +6,9 @@ local M = {}
 
 --- Decode JSON from a table of strings into a table of objects.
 --- @param tbl table
+--- @param construct_invalid boolean
 --- @return table
-function M.decode_from_table(tbl)
+function M.decode_from_table(tbl, construct_invalid)
   local jsonlines = {}
   for _, line in ipairs(tbl) do
     if string.match(line, "^%s*{") then -- must start with the `{` character
@@ -19,7 +20,10 @@ function M.decode_from_table(tbl)
         logger.warn("Failed to decode JSON line: " .. line)
       end
     else
-      -- vim.notify("Not valid JSON: " .. line, vim.log.levels.DEBUG)
+      logger.debug({ "Not valid JSON:", line })
+      if construct_invalid then
+        table.insert(jsonlines, { Action = "output", Output = line })
+      end
     end
   end
   return jsonlines
@@ -40,7 +44,7 @@ function M.decode_from_string(str)
     current_object = current_object .. line
   end
   table.insert(tbl, current_object)
-  return M.decode_from_table(tbl)
+  return M.decode_from_table(tbl, false)
 end
 
 return M
diff --git a/lua/neotest-golang/process.lua b/lua/neotest-golang/process.lua
index 2d836be9..a3ddcb3a 100644
--- a/lua/neotest-golang/process.lua
+++ b/lua/neotest-golang/process.lua
@@ -16,7 +16,6 @@ local lib = require("neotest-golang.lib")
 --- @field golist_data table<string, string> Filepath to 'go list' JSON data (lua table). -- TODO: rename to golist_data
 --- @field parse_test_results boolean If true, parsing of test output will occur.
 --- @field test_output_json_filepath? string Gotestsum JSON filepath.
---- @field dummy_test? boolean Temporary workaround before supporting position type 'test'.
 
 --- @class TestData
 --- @field status neotest.ResultStatus
@@ -50,7 +49,7 @@ function M.test_results(spec, result, tree)
       ---@type neotest.ResultStatus
       status = "skipped",
     }
-    return results -- return early, fail fast
+    return results -- return early, used by e.g. debugging
   end
 
   --- The Neotest position tree node for this execution.
@@ -70,7 +69,6 @@ function M.test_results(spec, result, tree)
   --- The runner to use for running tests.
   --- @type string
   local runner = options.get().runner
-
   --- The raw output from the test command.
   --- @type table
   local raw_output = {}
@@ -81,41 +79,62 @@ function M.test_results(spec, result, tree)
   end
   logger.debug({ "Raw 'go test' output: ", raw_output })
 
-  local gotest_output = lib.json.decode_from_table(raw_output)
-  logger.debug({ "Parsed 'go test' output: ", gotest_output })
-
-  --- The 'go list -json' output, converted into a lua table.
-  local golist_output = context.golist_data
-  logger.debug({ "Parsed 'go list' output: ", golist_output })
-
+  --- Final Neotest results, the way Neotest wants it returned.
   --- @type table<string, neotest.Result>
   local neotest_result = {}
-
   --- Test command (e.g. 'go test') status.
   --- @type neotest.ResultStatus
   local test_command_status = "skipped"
+  --- Go test output,
+  --- @type table
+  local gotest_output = {}
+  --- Test command output.
+  --- @type string
+  local test_command_output_path = vim.fs.normalize(async.fn.tempname())
+
   if result.code == 0 then
     test_command_status = "passed"
+    --- Parse raw output into a table.
+    gotest_output = lib.json.decode_from_table(raw_output, false)
+    logger.debug({ "Parsed 'go test' output: ", gotest_output })
+    async.fn.writefile(
+      M.extract_gotest_output(gotest_output),
+      test_command_output_path
+    )
+    -- register properties on the directory node that was run
+    neotest_result[pos.id] = {
+      status = test_command_status,
+      output = test_command_output_path,
+    }
   else
     test_command_status = "failed"
-  end
-
-  --- Full 'go test' output (parsed from JSON).
-  --- @type table
-  local o = {}
-  local test_command_output_path = vim.fs.normalize(async.fn.tempname())
-  for _, line in ipairs(gotest_output) do
-    if line.Action == "output" then
-      table.insert(o, line.Output)
+    if runner == "go" then
+      --- Parse raw output into a table.
+      gotest_output = lib.json.decode_from_table(raw_output, true)
+      logger.debug({ "Parsed 'go test' output: ", gotest_output })
+      async.fn.writefile(
+        M.extract_gotest_output(gotest_output),
+        test_command_output_path
+      )
+    elseif runner == "gotestsum" then
+      -- Gotestsum unfortunately does not write the stderr output into its JSON output.
+      async.fn.writefile(
+        { "Failed to run test. Compilation error?" },
+        test_command_output_path
+      )
     end
+
+    -- register properties on the directory node that was run
+    neotest_result[pos.id] = {
+      status = test_command_status,
+      output = test_command_output_path,
+    }
+    return neotest_result -- return early, fail fast
   end
-  async.fn.writefile(o, test_command_output_path)
 
-  -- register properties on the directory node that was run
-  neotest_result[pos.id] = {
-    status = test_command_status,
-    output = test_command_output_path,
-  }
+  --- The 'go list -json' output, converted into a lua table.
+  local golist_output = context.golist_data
+  logger.debug({ "Parsed 'go list' output: ", golist_output })
 
   --- Internal data structure to store test result data.
   --- @type table<string, TestData>
@@ -137,6 +156,19 @@ function M.test_results(spec, result, tree)
   return neotest_result
 end
 
+--- Extract the Output-type parts of the 'go test' output.
+--- @param gotest_output table
+--- @return table
+function M.extract_gotest_output(gotest_output)
+  local o = {}
+  for _, line in ipairs(gotest_output) do
+    if line.Action == "output" then
+      table.insert(o, line.Output)
+    end
+  end
+  return o
+end
+
 --- Aggregate neotest data and 'go test' output data.
 --- @param tree neotest.Tree
 --- @param gotest_output table