diff --git a/caddytest/caddytest.go b/caddytest/caddytest.go
index 3de5b96b0..9a89d6b1e 100644
--- a/caddytest/caddytest.go
+++ b/caddytest/caddytest.go
@@ -11,6 +11,7 @@ import (
 	"net/http"
 	"net/http/cookiejar"
 	"os"
+	"strconv"
 	"strings"
 	"time"
 
@@ -22,8 +23,6 @@ import (
 
 // Defaults store any configuration required to make the tests run
 type Defaults struct {
-	// Port we expect caddy to listening on
-	AdminPort int
 	// Certificates we expect to be loaded before attempting to run the tests
 	Certificates []string
 	// TestRequestTimeout is the time to wait for a http request to
@@ -34,7 +33,6 @@ type Defaults struct {
 
 // Default testing values
 var Default = Defaults{
-	AdminPort:          2999, // different from what a real server also running on a developer's machine might be
 	Certificates:       []string{"/caddy.localhost.crt", "/caddy.localhost.key"},
 	TestRequestTimeout: 5 * time.Second,
 	LoadRequestTimeout: 5 * time.Second,
@@ -42,9 +40,12 @@ var Default = Defaults{
 
 // Tester represents an instance of a test client.
 type Tester struct {
-	Client         *http.Client
+	Client *http.Client
+
+	adminPort      int
 	configLoaded   bool
 	configFileName string
+	envFileName    string
 }
 
 // NewTester will create a new testing client with an attached cookie jar
@@ -86,26 +87,37 @@ func (tc *Tester) LaunchCaddy() error {
 func (tc *Tester) CleanupCaddy() error {
 	// now shutdown the server, since the test is done.
 	defer func() {
-		// try to remove the tmp config file we created
-		os.Remove(tc.configFileName)
+		// try to remove  pthe tmp config file we created
+		if tc.configFileName != "" {
+			os.Remove(tc.configFileName)
+		}
+		if tc.envFileName != "" {
+			os.Remove(tc.envFileName)
+		}
 	}()
-	_, err := http.Post(fmt.Sprintf("http://localhost:%d/stop", Default.AdminPort), "", nil)
+	resp, err := http.Post(fmt.Sprintf("http://localhost:%d/stop", tc.adminPort), "", nil)
 	if err != nil {
 		return fmt.Errorf("couldn't stop caddytest server: %w", err)
 	}
+	resp.Body.Close()
 	for retries := 0; retries < 10; retries++ {
-		if isCaddyAdminRunning() != nil {
+		if tc.isCaddyAdminRunning() != nil {
 			return nil
 		}
 		time.Sleep(100 * time.Millisecond)
 	}
 
 	return fmt.Errorf("timed out waiting for caddytest server to stop")
-
 }
 
 // LoadConfig loads the config to the tester server and also ensures that the config was loaded
+// it should not be run
 func (tc *Tester) LoadConfig(rawConfig string, configType string) error {
+	if tc.adminPort == 0 {
+		return fmt.Errorf("load config called where startServer didnt succeed")
+	}
+	// replace special testing placeholders so we can have our admin api be on a random port
+	rawConfig = strings.ReplaceAll(rawConfig, "{$TESTING_ADMIN_API}", fmt.Sprintf("localhost:%d", tc.adminPort))
 	// normalize JSON config
 	if configType == "json" {
 		var conf any
@@ -122,7 +134,7 @@ func (tc *Tester) LoadConfig(rawConfig string, configType string) error {
 		Timeout: Default.LoadRequestTimeout,
 	}
 	start := time.Now()
-	req, err := http.NewRequest("POST", fmt.Sprintf("http://localhost:%d/load", Default.AdminPort), strings.NewReader(rawConfig))
+	req, err := http.NewRequest("POST", fmt.Sprintf("http://localhost:%d/load", tc.adminPort), strings.NewReader(rawConfig))
 	if err != nil {
 		return fmt.Errorf("failed to create request. %w", err)
 	}
@@ -162,7 +174,7 @@ func (tc *Tester) GetCurrentConfig(receiver any) error {
 		Timeout: Default.LoadRequestTimeout,
 	}
 
-	resp, err := client.Get(fmt.Sprintf("http://localhost:%d/config/", Default.AdminPort))
+	resp, err := client.Get(fmt.Sprintf("http://localhost:%d/config/", tc.adminPort))
 	if err != nil {
 		return err
 	}
@@ -178,48 +190,73 @@ func (tc *Tester) GetCurrentConfig(receiver any) error {
 	return nil
 }
 
-const initConfig = `{
-	admin localhost:2999
+func getFreePort() (int, error) {
+	lr, err := net.Listen("tcp", "localhost:0")
+	if err != nil {
+		return 0, err
+	}
+	port := strings.Split(lr.Addr().String(), ":")
+	if len(port) < 2 {
+		return 0, fmt.Errorf("no port available")
+	}
+	i, err := strconv.Atoi(port[1])
+	if err != nil {
+		return 0, err
+	}
+	err = lr.Close()
+	if err != nil {
+		return 0, fmt.Errorf("failed to close listener: %w", err)
+	}
+	return i, nil
 }
-`
 
 // launches caddy, and then ensures the Caddy sub-process is running.
 func (tc *Tester) startServer() error {
-	if isCaddyAdminRunning() == nil {
+	if tc.isCaddyAdminRunning() == nil {
 		return fmt.Errorf("caddy test admin port still in use")
 	}
-	// setup the init config file, and set the cleanup afterwards
-	f, err := os.CreateTemp("", "")
+	a, err := getFreePort()
 	if err != nil {
-		return err
+		return fmt.Errorf("could not find a open port to listen on: %w", err)
 	}
-	tc.configFileName = f.Name()
+	tc.adminPort = a
+	// setup the init config file, and set the cleanup afterwards
+	{
+		f, err := os.CreateTemp("", "")
+		if err != nil {
+			return err
+		}
+		tc.configFileName = f.Name()
 
-	if _, err := f.WriteString(initConfig); err != nil {
-		return err
+		initConfig := fmt.Sprintf(`{
+	admin localhost:%d
+}`, a)
+		if _, err := f.WriteString(initConfig); err != nil {
+			return err
+		}
 	}
 
 	// start inprocess caddy server
 	go func() {
-		caddycmd.MainForTesting("run", "--config", tc.configFileName, "--adapter", "caddyfile")
+		_ = caddycmd.MainForTesting("run", "--config", tc.configFileName, "--adapter", "caddyfile")
 	}()
 	// wait for caddy admin api to start. it should happen quickly.
-	for retries := 10; retries > 0 && isCaddyAdminRunning() != nil; retries-- {
+	for retries := 10; retries > 0 && tc.isCaddyAdminRunning() != nil; retries-- {
 		time.Sleep(100 * time.Millisecond)
 	}
 
 	// one more time to return the error
-	return isCaddyAdminRunning()
+	return tc.isCaddyAdminRunning()
 }
 
-func isCaddyAdminRunning() error {
+func (tc *Tester) isCaddyAdminRunning() error {
 	// assert that caddy is running
 	client := &http.Client{
 		Timeout: Default.LoadRequestTimeout,
 	}
-	resp, err := client.Get(fmt.Sprintf("http://localhost:%d/config/", Default.AdminPort))
+	resp, err := client.Get(fmt.Sprintf("http://localhost:%d/config/", tc.adminPort))
 	if err != nil {
-		return fmt.Errorf("caddy integration test caddy server not running. Expected to be listening on localhost:%d", Default.AdminPort)
+		return fmt.Errorf("caddy integration test caddy server not running. Expected to be listening on localhost:%d", tc.adminPort)
 	}
 	resp.Body.Close()
 
diff --git a/caddytest/caddytest_assert.go b/caddytest/caddytest_assert.go
index 8587abaed..23054424d 100644
--- a/caddytest/caddytest_assert.go
+++ b/caddytest/caddytest_assert.go
@@ -9,8 +9,9 @@ import (
 	"testing"
 
 	"github.com/aryann/difflib"
-	"github.com/caddyserver/caddy/v2/caddyconfig"
 	"github.com/stretchr/testify/require"
+
+	"github.com/caddyserver/caddy/v2/caddyconfig"
 )
 
 // AssertLoadError will load a config and expect an error
@@ -24,7 +25,7 @@ func AssertLoadError(t *testing.T, rawConfig string, configType string, expected
 	if !strings.Contains(err.Error(), expectedError) {
 		t.Errorf("expected error \"%s\" but got \"%s\"", expectedError, err.Error())
 	}
-	tc.CleanupCaddy()
+	_ = tc.CleanupCaddy()
 }
 
 // CompareAdapt adapts a config and then compares it against an expected result
diff --git a/caddytest/caddytest_test.go b/caddytest/caddytest_test.go
index 589c33ea6..1cca9ff0f 100644
--- a/caddytest/caddytest_test.go
+++ b/caddytest/caddytest_test.go
@@ -68,7 +68,7 @@ func TestLoadUnorderedJSON(t *testing.T) {
 			}
 		},
 		"admin": {
-			"listen": "localhost:2999"
+			"listen": "{$TESTING_ADMIN_API}"
 		},
 		"apps": {
 			"pki": {
diff --git a/caddytest/integration/acme_test.go b/caddytest/integration/acme_test.go
index 9697cf955..8cd3220df 100644
--- a/caddytest/integration/acme_test.go
+++ b/caddytest/integration/acme_test.go
@@ -28,7 +28,7 @@ func TestACMEServerWithDefaults(t *testing.T) {
 	tester.LoadConfig(`
 	{
 		skip_install_trust
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 		https_port    9443
 		local_certs
@@ -96,7 +96,7 @@ func TestACMEServerWithMismatchedChallenges(t *testing.T) {
 	tester.LoadConfig(`
 	{
 		skip_install_trust
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 		https_port    9443
 		local_certs
diff --git a/caddytest/integration/acmeserver_test.go b/caddytest/integration/acmeserver_test.go
index e3ce29ac0..604a59f76 100644
--- a/caddytest/integration/acmeserver_test.go
+++ b/caddytest/integration/acmeserver_test.go
@@ -20,7 +20,7 @@ func TestACMEServerDirectory(t *testing.T) {
 	{
 		skip_install_trust
 		local_certs
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 		https_port    9443
 		pki {
@@ -46,7 +46,7 @@ func TestACMEServerAllowPolicy(t *testing.T) {
 	{
 		skip_install_trust
 		local_certs
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 		https_port    9443
 		pki {
@@ -132,7 +132,7 @@ func TestACMEServerDenyPolicy(t *testing.T) {
 	{
 		skip_install_trust
 		local_certs
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 		https_port    9443
 		pki {
diff --git a/caddytest/integration/autohttps_test.go b/caddytest/integration/autohttps_test.go
index 993fa2b9a..89070b29e 100644
--- a/caddytest/integration/autohttps_test.go
+++ b/caddytest/integration/autohttps_test.go
@@ -11,7 +11,7 @@ func TestAutoHTTPtoHTTPSRedirectsImplicitPort(t *testing.T) {
 	tester := caddytest.StartHarness(t)
 	tester.LoadConfig(`
 	{
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		skip_install_trust
 		http_port     9080
 		https_port    9443
@@ -28,7 +28,7 @@ func TestAutoHTTPtoHTTPSRedirectsExplicitPortSameAsHTTPSPort(t *testing.T) {
 	tester.LoadConfig(`
 	{
 		skip_install_trust
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 		https_port    9443
 	}
@@ -44,7 +44,7 @@ func TestAutoHTTPtoHTTPSRedirectsExplicitPortDifferentFromHTTPSPort(t *testing.T
 	tester.LoadConfig(`
 	{
 		skip_install_trust
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 		https_port    9443
 	}
@@ -60,7 +60,7 @@ func TestAutoHTTPRedirectsWithHTTPListenerFirstInAddresses(t *testing.T) {
 	tester.LoadConfig(`
 {
   "admin": {
-	"listen": "localhost:2999"
+	"listen": "{$TESTING_ADMIN_API}"
   },
   "apps": {
     "http": {
@@ -102,7 +102,7 @@ func TestAutoHTTPRedirectsInsertedBeforeUserDefinedCatchAll(t *testing.T) {
 	tester.LoadConfig(`
 	{
 		skip_install_trust
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 		https_port    9443
 		local_certs
@@ -127,7 +127,7 @@ func TestAutoHTTPRedirectsInsertedBeforeUserDefinedCatchAllWithNoExplicitHTTPSit
 	tester.LoadConfig(`
 	{
 		skip_install_trust
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 		https_port    9443
 		local_certs
diff --git a/caddytest/integration/caddyfile_test.go b/caddytest/integration/caddyfile_test.go
index 44c28cd58..647d6b7ce 100644
--- a/caddytest/integration/caddyfile_test.go
+++ b/caddytest/integration/caddyfile_test.go
@@ -13,7 +13,7 @@ func TestRespond(t *testing.T) {
 	tester := caddytest.StartHarness(t)
 	tester.LoadConfig(`
   {
-    admin localhost:2999
+    admin {$TESTING_ADMIN_API}
     http_port     9080
     https_port    9443
     grace_period  1ns
@@ -35,7 +35,7 @@ func TestRedirect(t *testing.T) {
 	tester := caddytest.StartHarness(t)
 	tester.LoadConfig(`
   {
-    admin localhost:2999
+    admin {$TESTING_ADMIN_API}
     http_port     9080
     https_port    9443
     grace_period  1ns
@@ -85,7 +85,7 @@ func TestReadCookie(t *testing.T) {
 	tester.LoadConfig(`
   {
     skip_install_trust
-    admin localhost:2999
+    admin {$TESTING_ADMIN_API}
     http_port     9080
     https_port    9443
     grace_period  1ns
@@ -110,7 +110,7 @@ func TestReplIndex(t *testing.T) {
 	tester.LoadConfig(`
   {
     skip_install_trust
-    admin localhost:2999
+    admin {$TESTING_ADMIN_API}
     http_port     9080
     https_port    9443
     grace_period  1ns
@@ -485,7 +485,7 @@ func TestUriReplace(t *testing.T) {
 
 	tester.LoadConfig(`
 	{
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 	}
 	:9080
@@ -502,7 +502,7 @@ func TestUriOps(t *testing.T) {
 
 	tester.LoadConfig(`
 	{
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 	}
 	:9080
@@ -527,7 +527,7 @@ func TestHttpRequestLocalPortPlaceholder(t *testing.T) {
 
 	tester.LoadConfig(`
 	{
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 	}
 	:9080
@@ -541,7 +541,7 @@ func TestSetThenAddQueryParams(t *testing.T) {
 
 	tester.LoadConfig(`
 	{
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 	}
 	:9080
@@ -558,7 +558,7 @@ func TestSetThenDeleteParams(t *testing.T) {
 
 	tester.LoadConfig(`
 	{
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 	}
 	:9080
@@ -575,7 +575,7 @@ func TestRenameAndOtherOps(t *testing.T) {
 
 	tester.LoadConfig(`
 	{
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 	}
 	:9080
@@ -593,7 +593,7 @@ func TestReplaceOps(t *testing.T) {
 
 	tester.LoadConfig(`
 	{
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 	}
 	:9080
@@ -607,7 +607,7 @@ func TestReplaceWithReplacementPlaceholder(t *testing.T) {
 	tester := caddytest.StartHarness(t)
 	tester.LoadConfig(`
 	{
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 	}
 	:9080
@@ -615,14 +615,13 @@ func TestReplaceWithReplacementPlaceholder(t *testing.T) {
 	respond "{query}"`, "caddyfile")
 
 	tester.AssertGetResponse("http://localhost:9080/endpoint?placeholder=baz&foo=bar", 200, "foo=baz&placeholder=baz")
-
 }
 
 func TestReplaceWithKeyPlaceholder(t *testing.T) {
 	tester := caddytest.StartHarness(t)
 	tester.LoadConfig(`
 	{
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 	}
 	:9080
@@ -636,7 +635,7 @@ func TestPartialReplacement(t *testing.T) {
 	tester := caddytest.StartHarness(t)
 	tester.LoadConfig(`
 	{
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 	}
 	:9080
@@ -650,7 +649,7 @@ func TestNonExistingSearch(t *testing.T) {
 	tester := caddytest.StartHarness(t)
 	tester.LoadConfig(`
 	{
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 	}
 	:9080
@@ -665,7 +664,7 @@ func TestReplaceAllOps(t *testing.T) {
 
 	tester.LoadConfig(`
 	{
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 	}
 	:9080
@@ -680,7 +679,7 @@ func TestUriOpsBlock(t *testing.T) {
 
 	tester.LoadConfig(`
 	{
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 	}
 	:9080
@@ -697,7 +696,7 @@ func TestUriOpsBlock(t *testing.T) {
 func TestHandleErrorSimpleCodes(t *testing.T) {
 	tester := caddytest.StartHarness(t)
 	tester.LoadConfig(`{
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 	}
 	localhost:9080 {
@@ -717,7 +716,7 @@ func TestHandleErrorSimpleCodes(t *testing.T) {
 func TestHandleErrorRange(t *testing.T) {
 	tester := caddytest.StartHarness(t)
 	tester.LoadConfig(`{
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 	}
 	localhost:9080 {
@@ -737,7 +736,7 @@ func TestHandleErrorRange(t *testing.T) {
 func TestHandleErrorSort(t *testing.T) {
 	tester := caddytest.StartHarness(t)
 	tester.LoadConfig(`{
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 	}
 	localhost:9080 {
@@ -761,7 +760,7 @@ func TestHandleErrorSort(t *testing.T) {
 func TestHandleErrorRangeAndCodes(t *testing.T) {
 	tester := caddytest.StartHarness(t)
 	tester.LoadConfig(`{
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 	}
 	localhost:9080 {
diff --git a/caddytest/integration/handler_test.go b/caddytest/integration/handler_test.go
index 62b37939f..11d852420 100644
--- a/caddytest/integration/handler_test.go
+++ b/caddytest/integration/handler_test.go
@@ -13,7 +13,7 @@ func TestBrowse(t *testing.T) {
 	tester.LoadConfig(`
 	{
 		skip_install_trust
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 		https_port    9443
 		grace_period  1ns
@@ -36,7 +36,7 @@ func TestRespondWithJSON(t *testing.T) {
 	tester.LoadConfig(`
 	{
 		skip_install_trust
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 		https_port    9443
 		grace_period  1ns
diff --git a/caddytest/integration/intercept_test.go b/caddytest/integration/intercept_test.go
index ef33f1cd8..2e4d780ca 100644
--- a/caddytest/integration/intercept_test.go
+++ b/caddytest/integration/intercept_test.go
@@ -10,7 +10,7 @@ func TestIntercept(t *testing.T) {
 	tester := caddytest.StartHarness(t)
 	tester.LoadConfig(`{
 			skip_install_trust
-			admin localhost:2999
+			admin {$TESTING_ADMIN_API}
 			http_port     9080
 			https_port    9443
 			grace_period  1ns
diff --git a/caddytest/integration/leafcertloaders_test.go b/caddytest/integration/leafcertloaders_test.go
index 39501fe5b..90c396f48 100644
--- a/caddytest/integration/leafcertloaders_test.go
+++ b/caddytest/integration/leafcertloaders_test.go
@@ -11,7 +11,7 @@ func TestLeafCertLoaders(t *testing.T) {
 	tester.LoadConfig(`
 	{
 		"admin": {
-			"listen": "localhost:2999"
+			"listen": "{$TESTING_ADMIN_API}"
 		},
 		"apps": {
 			"http": {
diff --git a/caddytest/integration/listener_test.go b/caddytest/integration/listener_test.go
index b2e327b04..24b865093 100644
--- a/caddytest/integration/listener_test.go
+++ b/caddytest/integration/listener_test.go
@@ -32,7 +32,7 @@ func setupListenerWrapperTest(t *testing.T, handlerFunc http.HandlerFunc) *caddy
 	tester.LoadConfig(fmt.Sprintf(`
 	{
 		skip_install_trust
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 		https_port    9443
 		local_certs
diff --git a/caddytest/integration/map_test.go b/caddytest/integration/map_test.go
index c5e7d7d3d..ac20af45d 100644
--- a/caddytest/integration/map_test.go
+++ b/caddytest/integration/map_test.go
@@ -12,7 +12,7 @@ func TestMap(t *testing.T) {
 	tester := caddytest.StartHarness(t)
 	tester.LoadConfig(`{
 		skip_install_trust
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 		https_port    9443
 		grace_period  1ns
@@ -42,7 +42,7 @@ func TestMapRespondWithDefault(t *testing.T) {
 	tester := caddytest.StartHarness(t)
 	tester.LoadConfig(`{
 		skip_install_trust
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 		https_port    9443
 		}
@@ -71,7 +71,7 @@ func TestMapAsJSON(t *testing.T) {
 	tester.LoadConfig(`
 	{
 		"admin": {
-			"listen": "localhost:2999"
+			"listen": "{$TESTING_ADMIN_API}"
 		},
 		"apps": {
 			"pki": {
diff --git a/caddytest/integration/reverseproxy_test.go b/caddytest/integration/reverseproxy_test.go
index f165c2e5c..fdb742e8c 100644
--- a/caddytest/integration/reverseproxy_test.go
+++ b/caddytest/integration/reverseproxy_test.go
@@ -18,7 +18,7 @@ func TestSRVReverseProxy(t *testing.T) {
 	tester.LoadConfig(`
 	{
 		"admin": {
-			"listen": "localhost:2999"
+			"listen": "{$TESTING_ADMIN_API}"
 		},
 		"apps": {
 			"pki": {
@@ -91,7 +91,7 @@ func TestDialWithPlaceholderUnix(t *testing.T) {
 	tester.LoadConfig(`
 	{
 		"admin": {
-			"listen": "localhost:2999"
+			"listen": "{$TESTING_ADMIN_API}"
 		},
 		"apps": {
 			"pki": {
@@ -143,7 +143,7 @@ func TestReverseProxyWithPlaceholderDialAddress(t *testing.T) {
 	tester.LoadConfig(`
 	{
 		"admin": {
-			"listen": "localhost:2999"
+			"listen": "{$TESTING_ADMIN_API}"
 		},
 		"apps": {
 			"pki": {
@@ -237,7 +237,7 @@ func TestReverseProxyWithPlaceholderTCPDialAddress(t *testing.T) {
 	tester.LoadConfig(`
 	{
 		"admin": {
-			"listen": "localhost:2999"
+			"listen": "{$TESTING_ADMIN_API}"
 		},
 		"apps": {
 			"pki": {
@@ -331,7 +331,7 @@ func TestReverseProxyHealthCheck(t *testing.T) {
 	tester.LoadConfig(`
 	{
 		skip_install_trust
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 		https_port    9443
 		grace_period 1ns
@@ -398,7 +398,7 @@ func TestReverseProxyHealthCheckUnixSocket(t *testing.T) {
 	tester.LoadConfig(fmt.Sprintf(`
 	{
 		skip_install_trust
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 		https_port    9443
 		grace_period 1ns
@@ -456,7 +456,7 @@ func TestReverseProxyHealthCheckUnixSocketWithoutPort(t *testing.T) {
 	tester.LoadConfig(fmt.Sprintf(`
 	{
 		skip_install_trust
-		admin localhost:2999
+		admin {$TESTING_ADMIN_API}
 		http_port     9080
 		https_port    9443
 		grace_period 1ns
diff --git a/caddytest/integration/sni_test.go b/caddytest/integration/sni_test.go
index 7830bf725..e5aced6e9 100644
--- a/caddytest/integration/sni_test.go
+++ b/caddytest/integration/sni_test.go
@@ -11,7 +11,7 @@ func TestDefaultSNI(t *testing.T) {
 	tester := caddytest.StartHarness(t)
 	tester.LoadConfig(`{
 		"admin": {
-			"listen": "localhost:2999"
+			"listen": "{$TESTING_ADMIN_API}"
 		},
 		"apps": {
 			"http": {
@@ -111,7 +111,7 @@ func TestDefaultSNIWithNamedHostAndExplicitIP(t *testing.T) {
 	tester.LoadConfig(` 
 	{
 		"admin": {
-			"listen": "localhost:2999"
+			"listen": "{$TESTING_ADMIN_API}"
 		},
 		"apps": {
 			"http": {
@@ -215,7 +215,7 @@ func TestDefaultSNIWithPortMappingOnly(t *testing.T) {
 	tester.LoadConfig(` 
 	{
 		"admin": {
-			"listen": "localhost:2999"
+			"listen": "{$TESTING_ADMIN_API}"
 		},
 		"apps": {
 			"http": {
diff --git a/caddytest/integration/stream_test.go b/caddytest/integration/stream_test.go
index 77c9bdfce..e47697793 100644
--- a/caddytest/integration/stream_test.go
+++ b/caddytest/integration/stream_test.go
@@ -24,7 +24,7 @@ func TestH2ToH2CStream(t *testing.T) {
 	tester.LoadConfig(`
   {
 	"admin": {
-		"listen": "localhost:2999"
+		"listen": "{$TESTING_ADMIN_API}"
 	},
     "apps": {
       "http": {
@@ -208,7 +208,7 @@ func TestH2ToH1ChunkedResponse(t *testing.T) {
 	tester.LoadConfig(`
 {
 	"admin": {
-		"listen": "localhost:2999"
+		"listen": "{$TESTING_ADMIN_API}"
 	},
   "apps": {
     "http": {
diff --git a/caddytest/testing_harness.go b/caddytest/testing_harness.go
index f1743097b..c5af3f6f5 100644
--- a/caddytest/testing_harness.go
+++ b/caddytest/testing_harness.go
@@ -83,7 +83,7 @@ func (tc *TestHarness) init() {
 	tc.t.Cleanup(func() {
 		func() {
 			if tc.t.Failed() {
-				res, err := http.Get(fmt.Sprintf("http://localhost:%d/config/", Default.AdminPort))
+				res, err := http.Get(fmt.Sprintf("http://localhost:%d/config/", tc.tester.adminPort))
 				if err != nil {
 					tc.t.Log("unable to read the current config")
 					return