diff --git a/internal/2017/DayThree/code_test.go b/internal/2017/DayThree/code_test.go
new file mode 100644
index 0000000..b1842d6
--- /dev/null
+++ b/internal/2017/DayThree/code_test.go
@@ -0,0 +1,41 @@
+package daythree
+
+import "testing"
+
+func TestPartOne(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    int
+		expected int
+	}{
+		{
+			name:     "square 1 is 0 steps",
+			input:    1,
+			expected: 0,
+		},
+		{
+			name:     "square 12 is 3 steps",
+			input:    12,
+			expected: 3,
+		},
+		{
+			name:     "square 23 is 2 steps",
+			input:    23,
+			expected: 2,
+		},
+		{
+			name:     "square 1024 is 31 steps",
+			input:    1024,
+			expected: 31,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := PartOne(tt.input)
+			if got != tt.expected {
+				t.Errorf("PartOne() = %d, want %d", got, tt.expected)
+			}
+		})
+	}
+}