diff --git a/active_tcp_test.go b/active_tcp_test.go
index 7b79830..d26a1bd 100644
--- a/active_tcp_test.go
+++ b/active_tcp_test.go
@@ -160,6 +160,9 @@ func TestActiveTCP(t *testing.T) {
 			passiveAgent, err := NewAgent(cfg)
 			req.NoError(err)
 			req.NotNil(passiveAgent)
+			defer func() {
+				req.NoError(passiveAgent.Close())
+			}()
 
 			activeAgent, err := NewAgent(&AgentConfig{
 				CandidateTypes:        []CandidateType{CandidateTypeHost},
@@ -172,6 +175,9 @@ func TestActiveTCP(t *testing.T) {
 
 			req.NoError(err)
 			req.NotNil(activeAgent)
+			defer func() {
+				req.NoError(activeAgent.Close())
+			}()
 
 			passiveAgentConn, activeAgenConn := connect(t, passiveAgent, activeAgent)
 			req.NotNil(passiveAgentConn)
diff --git a/gather_test.go b/gather_test.go
index d9195d6..7cd6c1a 100644
--- a/gather_test.go
+++ b/gather_test.go
@@ -275,17 +275,22 @@ func TestSTUNConcurrency(t *testing.T) {
 		_ = listener.Close()
 	}()
 
+	tcpMux := NewTCPMuxDefault(
+		TCPMuxParams{
+			Listener:       listener,
+			Logger:         logging.NewDefaultLoggerFactory().NewLogger("ice"),
+			ReadBufferSize: 8,
+		},
+	)
+	defer func() {
+		_ = tcpMux.Close()
+	}()
+
 	agent, err := NewAgent(&AgentConfig{
 		NetworkTypes:   supportedNetworkTypes(),
 		Urls:           urls,
 		CandidateTypes: []CandidateType{CandidateTypeHost, CandidateTypeServerReflexive},
-		TCPMux: NewTCPMuxDefault(
-			TCPMuxParams{
-				Listener:       listener,
-				Logger:         logging.NewDefaultLoggerFactory().NewLogger("ice"),
-				ReadBufferSize: 8,
-			},
-		),
+		TCPMux:         tcpMux,
 	})
 	require.NoError(t, err)
 	defer func() {
@@ -770,10 +775,14 @@ func TestMultiTCPMuxUsage(t *testing.T) {
 		}()
 
 		expectedPorts = append(expectedPorts, port)
-		tcpMuxInstances = append(tcpMuxInstances, NewTCPMuxDefault(TCPMuxParams{
+		tcpMux := NewTCPMuxDefault(TCPMuxParams{
 			Listener:       listener,
 			ReadBufferSize: 8,
-		}))
+		})
+		defer func() {
+			_ = tcpMux.Close()
+		}()
+		tcpMuxInstances = append(tcpMuxInstances, tcpMux)
 	}
 
 	agent, err := NewAgent(&AgentConfig{
diff --git a/tcp_mux_multi_test.go b/tcp_mux_multi_test.go
index 7fb0a09..aaba0a7 100644
--- a/tcp_mux_multi_test.go
+++ b/tcp_mux_multi_test.go
@@ -46,6 +46,9 @@ func TestMultiTCPMux_Recv(t *testing.T) {
 					ReadBufferSize:  20,
 					WriteBufferSize: bufSize,
 				})
+				defer func() {
+					_ = tcpMux.Close()
+				}()
 				muxInstances = append(muxInstances, tcpMux)
 				require.NotNil(t, tcpMux.LocalAddr(), "tcpMux.LocalAddr() is nil")
 			}
@@ -114,6 +117,9 @@ func TestMultiTCPMux_NoDeadlockWhenClosingUnusedPacketConn(t *testing.T) {
 			Logger:         loggerFactory.NewLogger("ice"),
 			ReadBufferSize: 20,
 		})
+		defer func() {
+			_ = tcpMux.Close()
+		}()
 		tcpMuxInstances = append(tcpMuxInstances, tcpMux)
 	}
 	muxMulti := NewMultiTCPMuxDefault(tcpMuxInstances...)
@@ -150,6 +156,9 @@ func TestMultiTCPMux_GetConnByUfrag_FromAnyMux(t *testing.T) {
 		Logger:         logger,
 		ReadBufferSize: 8,
 	})
+	defer func() {
+		_ = mux1.Close()
+	}()
 
 	l2, err := net.ListenTCP("tcp", &net.TCPAddr{IP: net.IP{127, 0, 0, 1}, Port: 0})
 	require.NoError(t, err)
@@ -162,6 +171,9 @@ func TestMultiTCPMux_GetConnByUfrag_FromAnyMux(t *testing.T) {
 		Logger:         logger,
 		ReadBufferSize: 8,
 	})
+	defer func() {
+		_ = mux2.Close()
+	}()
 
 	multi := NewMultiTCPMuxDefault(mux1, mux2)
 	defer func() { _ = multi.Close() }()
@@ -221,6 +233,9 @@ func TestMultiTCPMux_Close_PropagatesError_FromWrappedMux(t *testing.T) {
 		Logger:         logger,
 		ReadBufferSize: 8,
 	})
+	defer func() {
+		_ = mux1.Close()
+	}()
 
 	// second mux: Close() returns injected error
 	l2, err := net.ListenTCP("tcp", &net.TCPAddr{IP: net.IP{127, 0, 0, 1}, Port: 0})
@@ -230,6 +245,9 @@ func TestMultiTCPMux_Close_PropagatesError_FromWrappedMux(t *testing.T) {
 		Logger:         logger,
 		ReadBufferSize: 8,
 	})
+	defer func() {
+		_ = mux2Real.Close()
+	}()
 	mux2 := &closeErrTCPMux{TCPMux: mux2Real, ret: errTCPMuxCloseBoom}
 
 	multi := NewMultiTCPMuxDefault(mux1, mux2)
@@ -249,6 +267,9 @@ func TestMultiTCPMux_Close_LastErrorWins_FromWrappedMuxes(t *testing.T) {
 		Logger:         logger,
 		ReadBufferSize: 8,
 	})
+	defer func() {
+		_ = mux1Real.Close()
+	}()
 	mux1 := &closeErrTCPMux{TCPMux: mux1Real, ret: errTCPMuxCloseFirst}
 
 	// second mux: error2 (last error should be returned)
@@ -259,6 +280,9 @@ func TestMultiTCPMux_Close_LastErrorWins_FromWrappedMuxes(t *testing.T) {
 		Logger:         logger,
 		ReadBufferSize: 8,
 	})
+	defer func() {
+		_ = mux2Real.Close()
+	}()
 	mux2 := &closeErrTCPMux{TCPMux: mux2Real, ret: errTCPMuxCloseSecond}
 
 	multi := NewMultiTCPMuxDefault(mux1, mux2)
diff --git a/tcp_mux_test.go b/tcp_mux_test.go
index b33e399..986b1b0 100644
--- a/tcp_mux_test.go
+++ b/tcp_mux_test.go
@@ -147,6 +147,9 @@ func TestTCPMux_FirstPacketTimeout(t *testing.T) {
 		ReadBufferSize:       20,
 		FirstStunBindTimeout: time.Second,
 	})
+	defer func() {
+		_ = tcpMux.Close()
+	}()
 
 	require.NotNil(t, tcpMux.LocalAddr(), "tcpMux.LocalAddr() is nil")
 
diff --git a/transport_test.go b/transport_test.go
index cdb4f6b..b16f54b 100644
--- a/transport_test.go
+++ b/transport_test.go
@@ -207,11 +207,17 @@ func pipe(t *testing.T, defaultConfig *AgentConfig) (*Conn, *Conn) {
 	aAgent, err := NewAgent(cfg)
 	require.NoError(t, err)
 	require.NoError(t, aAgent.OnConnectionStateChange(aNotifier))
+	t.Cleanup(func() {
+		require.NoError(t, aAgent.Close())
+	})
 
 	bAgent, err := NewAgent(cfg)
 	require.NoError(t, err)
 
 	require.NoError(t, bAgent.OnConnectionStateChange(bNotifier))
+	t.Cleanup(func() {
+		require.NoError(t, bAgent.Close())
+	})
 
 	aConn, bConn := connect(t, aAgent, bAgent)
 
@@ -240,10 +246,16 @@ func pipeWithTimeout(t *testing.T, disconnectTimeout time.Duration, iceKeepalive
 	aAgent, err := NewAgent(cfg)
 	require.NoError(t, err)
 	require.NoError(t, aAgent.OnConnectionStateChange(aNotifier))
+	t.Cleanup(func() {
+		require.NoError(t, aAgent.Close())
+	})
 
 	bAgent, err := NewAgent(cfg)
 	require.NoError(t, err)
 	require.NoError(t, bAgent.OnConnectionStateChange(bNotifier))
+	t.Cleanup(func() {
+		require.NoError(t, bAgent.Close())
+	})
 
 	aConn, bConn := connect(t, aAgent, bAgent)