Enhance Go testing support and add integration tests

build_defs/go.build_defs

@@ -847,10 +847,29 @@ def go_test(name:str, srcs:list, resources:list=None, data:list|dict=None, deps:
         import_path = "main",
         _generate_pkg_info = False,
     )
-    cmds, tools = _go_binary_cmds(name, static=static, definitions=definitions, gcov=cgo, test=True)
+    # Match go test: testing/testing.go:692 (Go 1.25.3) relies on testing.testing=true when linking tests.
+    testing_definition = "testing.testing=true"
+    if definitions is None:
+        test_definitions = [testing_definition]
+    elif isinstance(definitions, dict):
+        if "testing.testing" in definitions:
+            test_definitions = definitions
+        else:
+            test_definitions = definitions | {"testing.testing": "true"}
+    else:
+        if isinstance(definitions, str):
+            test_definitions = [definitions]
+        elif isinstance(definitions, list):
+            test_definitions = list(definitions)
+        else:
+            test_definitions = list(definitions)
+        if testing_definition not in test_definitions:
+            test_definitions.append(testing_definition)
+
+    cmds, tools = _go_binary_cmds(name, static=static, definitions=test_definitions, gcov=cgo, test=True)
 
 
-    test_cmd = f'$TEST {flags} 2>&1 | tee $TMP_DIR/test.results'
+    test_cmd = f'$TEST {flags} 2>&1 | tee -- "$TMP_DIR/test.results"'
     worker_cmd = f'$(worker {worker})' if worker else ""
     if worker_cmd:
         test_cmd = f'{worker_cmd} && {test_cmd} '

test/build_defs/e2e.build_defs

@@ -2,11 +2,16 @@ subinclude("///e2e//build_defs:e2e")
 
 _please_repo_e2e_test = please_repo_e2e_test
 
-def please_repo_e2e_test(name, expected_output=None, plz_command, repo, labels=[]):
+def please_repo_e2e_test(name, expected_output=None, plz_command, repo, labels=[], expect_output_contains=None):
+    plz_cmd = plz_command.replace("plz ", "plz -o please.PluginRepo:file://$TMP_DIR/$DATA_PLUGIN_REPO -o plugin.go.gotool:$TOOLS_GO -o plugin.go.pleasegotool:$TOOLS_PLEASE_GO ")
+    # Persist command output so subsequent assertions can inspect it while keeping the original exit code.
+    wrapped_plz_command = f"( {plz_cmd} >output 2>&1 ); STATUS=$?; cat output; exit $STATUS"
+
     return _please_repo_e2e_test(
         name = name,
         expected_output = expected_output,
-        plz_command = plz_command.replace("plz ", "plz -o please.PluginRepo:file://$TMP_DIR/$DATA_PLUGIN_REPO -o plugin.go.gotool:$TOOLS_GO -o plugin.go.pleasegotool:$TOOLS_PLEASE_GO "),
+        expect_output_contains = expect_output_contains,
+        plz_command = wrapped_plz_command,
         repo = repo,
         data = {
             "PLUGIN_REPO": ["//test:export"],

test/testing_definition/BUILD

@@ -1,4 +1,5 @@
 subinclude("//build_defs:go")
+subinclude("//test/build_defs:e2e")
 
 go_test(
     name = "testing_definition_test",
@@ -7,3 +8,12 @@ go_test(
         "///third_party/go/github.com_stretchr_testify//assert",
     ],
 )
+
+please_repo_e2e_test(
+    name = "testing_definition_integration_test",
+    plz_command = "plz test --show_all_output //sample:testing_flag_test -- -test.v",
+    repo = "test_repo",
+    expect_output_contains = {
+        "output": "testing.Testing() = true",
+    },
+)

test/testing_definition/test_repo/.plzconfig

@@ -0,0 +1,8 @@
+[Parse]
+BuildFileName = BUILD_FILE
+BuildFileName = BUILD
+PreloadSubincludes = ///go//build_defs:go
+
+[Plugin "go"]
+Target = //plugins:go
+Stdlib = //third_party/go:std

test/testing_definition/test_repo/plugins/BUILD_FILE

@@ -0,0 +1,4 @@
+plugin_repo(
+    name = "go",
+    revision = "master",
+)

test/testing_definition/test_repo/sample/BUILD_FILE

@@ -0,0 +1,4 @@
+go_test(
+    name = "testing_flag_test",
+    srcs = ["testing_flag_test.go"],
+)

test/testing_definition/test_repo/sample/testing_flag_test.go

@@ -0,0 +1,13 @@
+package sample
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestTestingFlag(t *testing.T) {
+	fmt.Printf("testing.Testing() = %v\n", testing.Testing())
+	if !testing.Testing() {
+		t.Fatalf("expected testing.Testing() to be true")
+	}
+}

test/testing_definition/test_repo/third_party/go/BUILD_FILE

@@ -0,0 +1,3 @@
+go_stdlib(
+    name = "std",
+)