diff --git a/i3bridge.go b/i3bridge.go
new file mode 100644
index 0000000..dedb9fc
--- /dev/null
+++ b/i3bridge.go
@@ -0,0 +1,21 @@
+package main
+
+import (
+	i3 "go.i3wm.org/i3/v4"
+)
+
+// I3Commander abstrait i3.RunCommand pour testabilite.
+type I3Commander interface {
+	RunCommand(command string) ([]i3.CommandResult, error)
+}
+
+// FuzzyMatch trouve la premiere session matchant query dans : label > branche > cwd.
+// Case-insensitive. Retourne nil si aucun match.
+func FuzzyMatch(query string, sessions []SessionInfo) *SessionInfo {
+	return nil
+}
+
+// SwitchToWorkspace bascule vers le workspace indique via i3 IPC.
+func SwitchToWorkspace(commander I3Commander, wsName string) error {
+	return nil
+}
diff --git a/i3bridge_test.go b/i3bridge_test.go
new file mode 100644
index 0000000..3e8f7d6
--- /dev/null
+++ b/i3bridge_test.go
@@ -0,0 +1,147 @@
+package main
+
+import (
+	"fmt"
+	"testing"
+
+	i3 "go.i3wm.org/i3/v4"
+)
+
+// --- Mock types ---
+
+type mockI3Commander struct {
+	lastCommand string
+	results     []i3.CommandResult
+	err         error
+}
+
+func (m *mockI3Commander) RunCommand(command string) ([]i3.CommandResult, error) {
+	m.lastCommand = command
+	return m.results, m.err
+}
+
+// --- FuzzyMatch tests ---
+
+func TestFuzzyMatchByLabel(t *testing.T) {
+	sessions := []SessionInfo{
+		{SessionID: "s1", Label: "review MR !456", GitBranch: "main", Cwd: "/home/user/project"},
+		{SessionID: "s2", Label: "auth work", GitBranch: "feat/other", Cwd: "/home/user/other"},
+	}
+
+	result := FuzzyMatch("review", sessions)
+	if result == nil {
+		t.Fatal("expected match, got nil")
+	}
+	if result.SessionID != "s1" {
+		t.Errorf("FuzzyMatch = session %q, want %q", result.SessionID, "s1")
+	}
+}
+
+func TestFuzzyMatchByBranch(t *testing.T) {
+	sessions := []SessionInfo{
+		{SessionID: "s1", Label: "", GitBranch: "feat/auth-flow", Cwd: "/home/user/project"},
+		{SessionID: "s2", Label: "", GitBranch: "main", Cwd: "/home/user/other"},
+	}
+
+	result := FuzzyMatch("auth", sessions)
+	if result == nil {
+		t.Fatal("expected match, got nil")
+	}
+	if result.SessionID != "s1" {
+		t.Errorf("FuzzyMatch = session %q, want %q", result.SessionID, "s1")
+	}
+}
+
+func TestFuzzyMatchByCwd(t *testing.T) {
+	sessions := []SessionInfo{
+		{SessionID: "s1", Label: "", GitBranch: "main", Cwd: "/home/pierre/Code/vibe/vmux"},
+		{SessionID: "s2", Label: "", GitBranch: "main", Cwd: "/home/pierre/Code/other"},
+	}
+
+	result := FuzzyMatch("vmux", sessions)
+	if result == nil {
+		t.Fatal("expected match, got nil")
+	}
+	if result.SessionID != "s1" {
+		t.Errorf("FuzzyMatch = session %q, want %q", result.SessionID, "s1")
+	}
+}
+
+func TestFuzzyMatchPriority(t *testing.T) {
+	// Label match should win over branch match
+	sessions := []SessionInfo{
+		{SessionID: "s1", Label: "auth", GitBranch: "main", Cwd: "/home/user/project"},
+		{SessionID: "s2", Label: "", GitBranch: "auth", Cwd: "/home/user/other"},
+	}
+
+	result := FuzzyMatch("auth", sessions)
+	if result == nil {
+		t.Fatal("expected match, got nil")
+	}
+	if result.SessionID != "s1" {
+		t.Errorf("FuzzyMatch = session %q, want %q (label should win over branch)", result.SessionID, "s1")
+	}
+}
+
+func TestFuzzyMatchNoResult(t *testing.T) {
+	sessions := []SessionInfo{
+		{SessionID: "s1", Label: "review", GitBranch: "main", Cwd: "/home/user/project"},
+	}
+
+	result := FuzzyMatch("inexistant", sessions)
+	if result != nil {
+		t.Errorf("expected nil, got session %q", result.SessionID)
+	}
+}
+
+func TestFuzzyMatchCaseInsensitive(t *testing.T) {
+	sessions := []SessionInfo{
+		{SessionID: "s1", Label: "", GitBranch: "feat/auth-flow", Cwd: "/home/user/project"},
+	}
+
+	result := FuzzyMatch("AUTH", sessions)
+	if result == nil {
+		t.Fatal("expected case-insensitive match, got nil")
+	}
+	if result.SessionID != "s1" {
+		t.Errorf("FuzzyMatch = session %q, want %q", result.SessionID, "s1")
+	}
+}
+
+// --- SwitchToWorkspace tests ---
+
+func TestSwitchToWorkspace(t *testing.T) {
+	mock := &mockI3Commander{
+		results: []i3.CommandResult{{Success: true}},
+	}
+
+	err := SwitchToWorkspace(mock, "3")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if mock.lastCommand != "workspace number 3" {
+		t.Errorf("command = %q, want %q", mock.lastCommand, "workspace number 3")
+	}
+}
+
+func TestSwitchToWorkspaceError(t *testing.T) {
+	mock := &mockI3Commander{
+		results: []i3.CommandResult{{Success: false, Error: "no such workspace"}},
+	}
+
+	err := SwitchToWorkspace(mock, "99")
+	if err == nil {
+		t.Fatal("expected error, got nil")
+	}
+}
+
+func TestSwitchToWorkspaceI3Error(t *testing.T) {
+	mock := &mockI3Commander{
+		err: fmt.Errorf("i3 connection lost"),
+	}
+
+	err := SwitchToWorkspace(mock, "1")
+	if err == nil {
+		t.Fatal("expected error, got nil")
+	}
+}