1 files changed, 103 insertions, 0 deletions
diff --git a/internal/llm/circuitbreaker_test.go b/internal/llm/circuitbreaker_test.go
new file mode 100644
index 0000000..17510b3
--- /dev/null
+++ b/internal/llm/circuitbreaker_test.go
@@ -0,0 +1,103 @@
+package llm
+
+import (
+	"testing"
+	"time"
+)
+
+func TestCircuitBreaker_NilIsNoOp(t *testing.T) {
+	var cb *circuitBreaker
+	if !cb.Allow() {
+		t.Fatal("nil breaker must allow")
+	}
+	// These must not panic on a nil receiver.
+	cb.recordFailure()
+	cb.recordSuccess()
+}
+
+func TestCircuitBreaker_TripsAfterThreshold(t *testing.T) {
+	cb := newCircuitBreaker(3, time.Minute)
+	for i := 0; i < 2; i++ {
+		cb.recordFailure()
+		if !cb.Allow() {
+			t.Fatalf("breaker should stay closed before threshold (i=%d)", i)
+		}
+	}
+	cb.recordFailure() // third failure trips it
+	if cb.Allow() {
+		t.Fatal("breaker should be open after threshold failures")
+	}
+}
+
+func TestCircuitBreaker_SuccessResets(t *testing.T) {
+	cb := newCircuitBreaker(2, time.Minute)
+	cb.recordFailure()
+	cb.recordSuccess()
+	cb.recordFailure() // only one failure since reset; should not trip
+	if !cb.Allow() {
+		t.Fatal("breaker should remain closed after success reset")
+	}
+}
+
+func TestCircuitBreaker_HalfOpenAllowsSingleProbe(t *testing.T) {
+	now := time.Unix(0, 0)
+	cb := newCircuitBreaker(1, 10*time.Second)
+	cb.now = func() time.Time { return now }
+
+	cb.recordFailure() // trips (threshold 1)
+	if cb.Allow() {
+		t.Fatal("should be open immediately after trip")
+	}
+
+	// Advance past cooldown: first Allow transitions to half-open and permits one probe.
+	now = now.Add(11 * time.Second)
+	if !cb.Allow() {
+		t.Fatal("expected half-open probe to be allowed")
+	}
+	// A second concurrent probe is rejected.
+	if cb.Allow() {
+		t.Fatal("second probe must be rejected while half-open")
+	}
+}
+
+func TestCircuitBreaker_HalfOpenProbeSuccessCloses(t *testing.T) {
+	now := time.Unix(0, 0)
+	cb := newCircuitBreaker(1, time.Second)
+	cb.now = func() time.Time { return now }
+
+	cb.recordFailure()
+	now = now.Add(2 * time.Second)
+	if !cb.Allow() {
+		t.Fatal("expected probe allowed")
+	}
+	cb.recordSuccess()
+	if !cb.Allow() {
+		t.Fatal("breaker should be closed after successful probe")
+	}
+}
+
+func TestCircuitBreaker_HalfOpenProbeFailureReopens(t *testing.T) {
+	now := time.Unix(0, 0)
+	cb := newCircuitBreaker(1, time.Second)
+	cb.now = func() time.Time { return now }
+
+	cb.recordFailure()
+	now = now.Add(2 * time.Second)
+	if !cb.Allow() {
+		t.Fatal("expected probe allowed")
+	}
+	cb.recordFailure() // probe failed: reopen
+	if cb.Allow() {
+		t.Fatal("breaker should reopen after failed probe")
+	}
+}
+
+func TestCircuitBreaker_ZeroThresholdNeverTrips(t *testing.T) {
+	cb := newCircuitBreaker(0, time.Minute)
+	for i := 0; i < 100; i++ {
+		cb.recordFailure()
+	}
+	if !cb.Allow() {
+		t.Fatal("threshold<=0 should never trip the breaker")
+	}
+}