From 3af635b6c3442462df947cf3ffcb053df73c2620 Mon Sep 17 00:00:00 2001
From: Joakim Olsson <joakim@unbound.se>
Date: Thu, 1 Jan 2026 15:27:53 +0100
Subject: [PATCH] test: add comprehensive validation and cursor test coverage

---
 pagination_test.go | 163 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 163 insertions(+)

diff --git a/pagination_test.go b/pagination_test.go
index 26a322d..19fca3b 100644
--- a/pagination_test.go
+++ b/pagination_test.go
@@ -1,6 +1,7 @@
 package pagination
 
 import (
+	"errors"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -144,3 +145,165 @@ func TestGetPage(t *testing.T) {
 		})
 	}
 }
+
+func TestValidate(t *testing.T) {
+	tests := []struct {
+		name    string
+		first   *int
+		after   *string
+		last    *int
+		before  *string
+		wantErr error
+	}{
+		{
+			name:    "valid first",
+			first:   ptr(10),
+			wantErr: nil,
+		},
+		{
+			name:    "valid last",
+			last:    ptr(10),
+			wantErr: nil,
+		},
+		{
+			name:    "first and last both provided",
+			first:   ptr(10),
+			last:    ptr(10),
+			wantErr: ErrFirstAndLastProvided,
+		},
+		{
+			name:    "negative first",
+			first:   ptr(-1),
+			wantErr: ErrFirstNegative,
+		},
+		{
+			name:    "negative last",
+			last:    ptr(-1),
+			wantErr: ErrLastNegative,
+		},
+		{
+			name:    "after and before both provided",
+			after:   ptr("MQ=="),
+			before:  ptr("Mg=="),
+			wantErr: ErrAfterAndBeforeProvided,
+		},
+		{
+			name:    "invalid after cursor",
+			after:   ptr("not-valid-base64!@#"),
+			wantErr: ErrInvalidAfterCursor,
+		},
+		{
+			name:    "invalid before cursor",
+			before:  ptr("not-valid-base64!@#"),
+			wantErr: ErrInvalidBeforeCursor,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := Validate(tt.first, tt.after, tt.last, tt.before)
+			if tt.wantErr != nil {
+				assert.True(t, errors.Is(err, tt.wantErr), "Validate() error = %v, wantErr %v", err, tt.wantErr)
+			} else {
+				assert.NoError(t, err)
+			}
+		})
+	}
+}
+
+func TestDecodeCursor(t *testing.T) {
+	tests := []struct {
+		name    string
+		cursor  *string
+		want    string
+		wantErr error
+	}{
+		{
+			name:    "nil cursor",
+			cursor:  nil,
+			want:    "",
+			wantErr: nil,
+		},
+		{
+			name:    "valid cursor",
+			cursor:  ptr("dGVzdA=="),
+			want:    "test",
+			wantErr: nil,
+		},
+		{
+			name:    "invalid base64",
+			cursor:  ptr("not-valid-base64!@#"),
+			want:    "",
+			wantErr: ErrInvalidCursor,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := DecodeCursor(tt.cursor)
+			if tt.wantErr != nil {
+				assert.True(t, errors.Is(err, tt.wantErr), "DecodeCursor() error = %v, wantErr %v", err, tt.wantErr)
+			} else {
+				assert.NoError(t, err)
+				assert.Equal(t, tt.want, got)
+			}
+		})
+	}
+}
+
+func TestValidateCursor(t *testing.T) {
+	tests := []struct {
+		name    string
+		cursor  *string
+		wantErr error
+	}{
+		{
+			name:    "nil cursor",
+			cursor:  nil,
+			wantErr: nil,
+		},
+		{
+			name:    "valid cursor",
+			cursor:  ptr("dGVzdA=="),
+			wantErr: nil,
+		},
+		{
+			name:    "invalid cursor",
+			cursor:  ptr("not-valid-base64!@#"),
+			wantErr: ErrInvalidCursor,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := ValidateCursor(tt.cursor)
+			if tt.wantErr != nil {
+				assert.True(t, errors.Is(err, tt.wantErr), "ValidateCursor() error = %v, wantErr %v", err, tt.wantErr)
+			} else {
+				assert.NoError(t, err)
+			}
+		})
+	}
+}
+
+func TestEncodeCursor(t *testing.T) {
+	tests := []struct {
+		name   string
+		cursor string
+		want   string
+	}{
+		{
+			name:   "simple string",
+			cursor: "test",
+			want:   "dGVzdA==",
+		},
+		{
+			name:   "empty string",
+			cursor: "",
+			want:   "",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := EncodeCursor(tt.cursor)
+			assert.Equal(t, tt.want, got)
+		})
+	}
+}