Added tests and fixed timestamp handling

cmds/timestamps/input_test.go

@@ -0,0 +1,113 @@
+package main
+
+import (
+	"testing"
+	"time"
+)
+
+func TestParse(t *testing.T) {
+	// Reference time: 2025-11-19T11:07:13Z
+	// Unix: 1763550433
+	refTime := time.Date(2025, 11, 19, 11, 7, 13, 0, time.UTC)
+
+	tests := []struct {
+		input    string
+		expected func() time.Time
+		desc     string
+	}{
+		{
+			input: "1763550433",
+			expected: func() time.Time {
+				return refTime
+			},
+			desc: "Unix timestamp",
+		},
+		{
+			input: "2025-11-19T11:07:13Z",
+			expected: func() time.Time {
+				return refTime
+			},
+			desc: "ISO 8601 UTC",
+		},
+		{
+			input: "2025-11-19T11:07:13",
+			expected: func() time.Time {
+				return time.Date(2025, 11, 19, 11, 7, 13, 0, time.Local)
+			},
+			desc: "ISO 8601 Local",
+		},
+		{
+			input: "2025-11-19 11:07:13Z",
+			expected: func() time.Time {
+				return refTime
+			},
+			desc: "Date Space Time Z",
+		},
+		{
+			input: "2025-11-19",
+			expected: func() time.Time {
+				return time.Date(2025, 11, 19, 0, 0, 0, 0, time.Local)
+			},
+			desc: "Date only Local",
+		},
+		{
+			input: "2025-11-19Z",
+			expected: func() time.Time {
+				return time.Date(2025, 11, 19, 0, 0, 0, 0, time.UTC)
+			},
+			desc: "Date only UTC",
+		},
+		{
+			input: "11:07:13",
+			expected: func() time.Time {
+				now := time.Now()
+				return time.Date(now.Year(), now.Month(), now.Day(), 11, 7, 13, 0, time.Local)
+			},
+			desc: "Time only Local",
+		},
+		{
+			input: "11:07:13Z",
+			expected: func() time.Time {
+				now := time.Now().In(time.UTC)
+				return time.Date(now.Year(), now.Month(), now.Day(), 11, 7, 13, 0, time.UTC)
+			},
+			desc: "Time only UTC",
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.desc, func(t *testing.T) {
+			res, err := Parse(tc.input)
+			if err != nil {
+				t.Fatalf("Parse(%q) error: %v", tc.input, err)
+			}
+			got, err := res.Time()
+			if err != nil {
+				t.Fatalf("res.Time() error: %v", err)
+			}
+
+			want := tc.expected()
+
+			// For "Time only" tests, there might be a slight race condition if the day changes between test execution and expected value generation.
+			// But practically it's fine.
+
+			if !got.Truncate(time.Second).Equal(want) {
+				t.Errorf("Parse(%q) = %v, want %v", tc.input, got, want)
+			}
+		})
+	}
+
+	t.Run("now", func(t *testing.T) {
+		res, err := Parse("now")
+		if err != nil {
+			t.Fatalf("Parse('now') error: %v", err)
+		}
+		got, err := res.Time()
+		if err != nil {
+			t.Fatalf("res.Time() error: %v", err)
+		}
+		if time.Since(got) > time.Second {
+			t.Errorf("Parse('now') = %v, want close to now", got)
+		}
+	})
+}