Unit test for turkish stemmer (#2128)

**What this PR does:**
- Adds a test file for the Snowball Turkish stemmer.
- Tests various Turkish words to ensure proper stemming.

**Why this is useful:**
- Improves test coverage for Turkish language support in Bleve.
- Ensures the Snowball stemmer works as expected for Turkish words.

**Notes:**
- This PR only adds a test file and does not modify any existing
functionality.

analysis/lang/tr/stemmer_tr_test.go

@@ -0,0 +1,115 @@
+//  Copyright (c) 2025 Couchbase, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 		http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tr
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/blevesearch/bleve/v2/analysis"
+	"github.com/blevesearch/bleve/v2/registry"
+)
+
+func TestSnowballTurkishStemmer(t *testing.T) {
+	tests := []struct {
+		input  analysis.TokenStream
+		output analysis.TokenStream
+	}{
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("kimsesizler"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("kimsesiz"),
+				},
+			},
+		},
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("kitaplar"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("kitap"),
+				},
+			},
+		},
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("arabanın"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("araba"),
+				},
+			},
+		},
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("bardaklar"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("bardak"),
+				},
+			},
+		},
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("kediye"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("kedi"),
+				},
+			},
+		},
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("yazdım"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("yaz"),
+				},
+			},
+		},
+	}
+
+	cache := registry.NewCache()
+	filter, err := cache.TokenFilterNamed(SnowballStemmerName)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, test := range tests {
+		actual := filter.Filter(test.input)
+		if !reflect.DeepEqual(actual, test.output) {
+			t.Errorf("expected %s, got %s", test.output[0].Term, actual[0].Term)
+		}
+	}
+}