diff --git a/db/metrics_test.go b/db/metrics_test.go
index c61314f19..53cb851c5 100644
--- a/db/metrics_test.go
+++ b/db/metrics_test.go
@@ -84,3 +84,142 @@ func TestCalculateAverageDays(t *testing.T) {
 		})
 	}
 }
+
+type mockDatabase struct {
+	completedDifferenceFn func(PaymentDateRange, string) []DateDifference
+}
+
+func (m *mockDatabase) CompletedDifference(r PaymentDateRange, workspace string) []DateDifference {
+	return m.completedDifferenceFn(r, workspace)
+}
+
+func (m *mockDatabase) CompletedDifferenceCount(r PaymentDateRange, workspace string) int64 {
+	list := m.CompletedDifference(r, workspace)
+	return int64(len(list))
+}
+
+func TestCompletedDifferenceCount(t *testing.T) {
+
+	tests := []struct {
+		name      string
+		dateRange PaymentDateRange
+		workspace string
+		mockData  []DateDifference
+		expected  int64
+	}{
+		{
+			name: "Standard Case",
+			dateRange: PaymentDateRange{
+				StartDate: "2023-01-01",
+				EndDate:   "2023-12-31",
+			},
+			workspace: "workspace1",
+			mockData:  []DateDifference{{Diff: 100}, {Diff: 200}, {Diff: 300}},
+			expected:  3,
+		},
+		{
+			name: "Empty Result",
+			dateRange: PaymentDateRange{
+				StartDate: "2023-01-01",
+				EndDate:   "2023-12-31",
+			},
+			workspace: "workspace2",
+			mockData:  []DateDifference{},
+			expected:  0,
+		},
+		{
+			name: "No Workspace Specified",
+			dateRange: PaymentDateRange{
+				StartDate: "2023-01-01",
+				EndDate:   "2023-12-31",
+			},
+			workspace: "",
+			mockData:  []DateDifference{{Diff: 100}, {Diff: 200}},
+			expected:  2,
+		},
+		{
+			name: "Single Day Range",
+			dateRange: PaymentDateRange{
+				StartDate: "2023-01-01",
+				EndDate:   "2023-01-01",
+			},
+			workspace: "workspace1",
+			mockData:  []DateDifference{{Diff: 100}},
+			expected:  1,
+		},
+		{
+			name: "Large Dataset",
+			dateRange: PaymentDateRange{
+				StartDate: "2023-01-01",
+				EndDate:   "2023-12-31",
+			},
+			workspace: "workspace1",
+			mockData:  make([]DateDifference, 1000),
+			expected:  1000,
+		},
+		{
+			name: "Invalid Date Range",
+			dateRange: PaymentDateRange{
+				StartDate: "2023-12-31",
+				EndDate:   "2023-01-01",
+			},
+			workspace: "workspace1",
+			mockData:  []DateDifference{},
+			expected:  0,
+		},
+		{
+			name:      "Null Date Range",
+			dateRange: PaymentDateRange{},
+			workspace: "workspace1",
+			mockData:  []DateDifference{},
+			expected:  0,
+		},
+		{
+			name: "Special Characters in Workspace",
+			dateRange: PaymentDateRange{
+				StartDate: "2023-01-01",
+				EndDate:   "2023-12-31",
+			},
+			workspace: "workspace!@#$%",
+			mockData:  []DateDifference{{Diff: 100}},
+			expected:  1,
+		},
+		{
+			name: "Maximum Date Range",
+			dateRange: PaymentDateRange{
+				StartDate: "1970-01-01",
+				EndDate:   "2099-12-31",
+			},
+			workspace: "workspace1",
+			mockData:  []DateDifference{{Diff: 100}, {Diff: 200}, {Diff: 300}},
+			expected:  3,
+		},
+		{
+			name: "Boundary Values",
+			dateRange: PaymentDateRange{
+				StartDate: "2023-01-01",
+				EndDate:   "2023-01-01",
+			},
+			workspace: "",
+			mockData:  []DateDifference{{Diff: 0}, {Diff: math.MaxFloat64}},
+			expected:  2,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+
+			mockDB := &mockDatabase{
+				completedDifferenceFn: func(r PaymentDateRange, workspace string) []DateDifference {
+					assert.Equal(t, tt.dateRange, r)
+					assert.Equal(t, tt.workspace, workspace)
+					return tt.mockData
+				},
+			}
+
+			result := mockDB.CompletedDifferenceCount(tt.dateRange, tt.workspace)
+
+			assert.Equal(t, tt.expected, result)
+		})
+	}
+}