GO-4459: Add pagination tests

cmd/api/pagination/pagination_test.go

@@ -0,0 +1,94 @@
+package pagination
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestPaginate(t *testing.T) {
+	type args struct {
+		records []int
+		offset  int
+		limit   int
+	}
+	tests := []struct {
+		name          string
+		args          args
+		wantPaginated []int
+		wantHasMore   bool
+	}{
+		{
+			name: "Offset=0, Limit=2 (first two items)",
+			args: args{
+				records: []int{1, 2, 3, 4, 5},
+				offset:  0,
+				limit:   2,
+			},
+			wantPaginated: []int{1, 2},
+			wantHasMore:   true, // items remain: [3,4,5]
+		},
+		{
+			name: "Offset=2, Limit=2 (middle slice)",
+			args: args{
+				records: []int{1, 2, 3, 4, 5},
+				offset:  2,
+				limit:   2,
+			},
+			wantPaginated: []int{3, 4},
+			wantHasMore:   true, // item 5 remains
+		},
+		{
+			name: "Offset=4, Limit=2 (tail of the slice)",
+			args: args{
+				records: []int{1, 2, 3, 4, 5},
+				offset:  4,
+				limit:   2,
+			},
+			wantPaginated: []int{5},
+			wantHasMore:   false,
+		},
+		{
+			name: "Offset > length (should return empty)",
+			args: args{
+				records: []int{1, 2, 3, 4, 5},
+				offset:  10,
+				limit:   2,
+			},
+			wantPaginated: []int{},
+			wantHasMore:   false,
+		},
+		{
+			name: "Limit > length (should return entire slice)",
+			args: args{
+				records: []int{1, 2, 3},
+				offset:  0,
+				limit:   10,
+			},
+			wantPaginated: []int{1, 2, 3},
+			wantHasMore:   false,
+		},
+		{
+			name: "Zero limit (no items returned)",
+			args: args{
+				records: []int{1, 2, 3, 4, 5},
+				offset:  1,
+				limit:   0,
+			},
+			wantPaginated: []int{},
+			wantHasMore:   true, // items remain: [2,3,4,5]
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			gotPaginated, gotHasMore := Paginate(tt.args.records, tt.args.offset, tt.args.limit)
+
+			if !reflect.DeepEqual(gotPaginated, tt.wantPaginated) {
+				t.Errorf("Paginate() gotPaginated = %v, want %v", gotPaginated, tt.wantPaginated)
+			}
+			if gotHasMore != tt.wantHasMore {
+				t.Errorf("Paginate() gotHasMore = %v, want %v", gotHasMore, tt.wantHasMore)
+			}
+		})
+	}
+}