1 files changed, 160 insertions, 0 deletions
diff --git a/internal/metrics/sample_test.go b/internal/metrics/sample_test.go
new file mode 100644
index 0000000..2ffd78b
--- /dev/null
+++ b/internal/metrics/sample_test.go
@@ -0,0 +1,160 @@
+package metrics
+
+import (
+	"testing"
+	"time"
+)
+
+func TestNewSample(t *testing.T) {
+	tests := []struct {
+		name      string
+		metric    string
+		labels    map[string]string
+		value     float64
+		timestamp time.Time
+		wantNil   bool
+	}{
+		{
+			name:      "with labels",
+			metric:    "test_metric",
+			labels:    map[string]string{"env": "prod", "host": "server1"},
+			value:     42.5,
+			timestamp: time.Now(),
+			wantNil:   false,
+		},
+		{
+			name:      "nil labels initialized",
+			metric:    "test_metric",
+			labels:    nil,
+			value:     100,
+			timestamp: time.Now(),
+			wantNil:   false,
+		},
+		{
+			name:      "empty labels",
+			metric:    "test_metric",
+			labels:    map[string]string{},
+			value:     0,
+			timestamp: time.Now(),
+			wantNil:   false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			sample := NewSample(tt.metric, tt.labels, tt.value, tt.timestamp)
+
+			if sample.MetricName != tt.metric {
+				t.Errorf("MetricName = %v, want %v", sample.MetricName, tt.metric)
+			}
+			if sample.Value != tt.value {
+				t.Errorf("Value = %v, want %v", sample.Value, tt.value)
+			}
+			if sample.Labels == nil {
+				t.Error("Labels should never be nil")
+			}
+			if !sample.Timestamp.Equal(tt.timestamp) {
+				t.Errorf("Timestamp = %v, want %v", sample.Timestamp, tt.timestamp)
+			}
+		})
+	}
+}
+
+func TestSample_Age(t *testing.T) {
+	tests := []struct {
+		name     string
+		sample   Sample
+		wantNear time.Duration
+	}{
+		{
+			name: "recent sample",
+			sample: Sample{
+				MetricName: "test",
+				Timestamp:  time.Now().Add(-5 * time.Minute),
+			},
+			wantNear: 5 * time.Minute,
+		},
+		{
+			name: "old sample",
+			sample: Sample{
+				MetricName: "test",
+				Timestamp:  time.Now().Add(-1 * time.Hour),
+			},
+			wantNear: 1 * time.Hour,
+		},
+		{
+			name: "very recent",
+			sample: Sample{
+				MetricName: "test",
+				Timestamp:  time.Now().Add(-10 * time.Second),
+			},
+			wantNear: 10 * time.Second,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			age := tt.sample.Age()
+			// Allow 1 second tolerance for test execution time
+			if age < tt.wantNear-time.Second || age > tt.wantNear+time.Second {
+				t.Errorf("Age() = %v, want near %v", age, tt.wantNear)
+			}
+		})
+	}
+}
+
+func TestSample_IsRecent(t *testing.T) {
+	threshold := 5 * time.Minute
+
+	tests := []struct {
+		name      string
+		sample    Sample
+		threshold time.Duration
+		want      bool
+	}{
+		{
+			name: "within threshold",
+			sample: Sample{
+				MetricName: "test",
+				Timestamp:  time.Now().Add(-2 * time.Minute),
+			},
+			threshold: threshold,
+			want:      true,
+		},
+		{
+			name: "beyond threshold",
+			sample: Sample{
+				MetricName: "test",
+				Timestamp:  time.Now().Add(-10 * time.Minute),
+			},
+			threshold: threshold,
+			want:      false,
+		},
+		{
+			name: "exactly at threshold",
+			sample: Sample{
+				MetricName: "test",
+				Timestamp:  time.Now().Add(-5 * time.Minute),
+			},
+			threshold: threshold,
+			want:      false,
+		},
+		{
+			name: "very recent",
+			sample: Sample{
+				MetricName: "test",
+				Timestamp:  time.Now().Add(-10 * time.Second),
+			},
+			threshold: threshold,
+			want:      true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := tt.sample.IsRecent(tt.threshold); got != tt.want {
+				t.Errorf("IsRecent() = %v, want %v (age: %v)", got, tt.want, tt.sample.Age())
+			}
+		})
+	}
+}