internal/mcp: move jsonschema out of mcp/internal

The jsonschema package is part of of the API of the mcp package,
so it should not be internal.

Change-Id: I9520797837329fc2cda09c2f46ec4d48d031b9d3
Reviewed-on: https://go-review.googlesource.com/c/tools/+/669996
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Robert Findley <rfindley@google.com>

jsonschema/validate_test.go

@@ -0,0 +1,82 @@
+// Copyright 2025 The Go MCP SDK Authors. All rights reserved.
+// Use of this source code is governed by an MIT-style
+// license that can be found in the LICENSE file.
+
+package jsonschema
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+// The test for validation uses the official test suite, expressed as a set of JSON files.
+// Each file is an array of group objects.
+
+// A testGroup consists of a schema and some tests on it.
+type testGroup struct {
+	Description string
+	Schema      *Schema
+	Tests       []test
+}
+
+// A test consists of a JSON instance to be validated and the expected result.
+type test struct {
+	Description string
+	Data        any
+	Valid       bool
+}
+
+func TestValidate(t *testing.T) {
+	files, err := filepath.Glob(filepath.FromSlash("testdata/draft2020-12/*.json"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(files) == 0 {
+		t.Fatal("no files")
+	}
+	for _, file := range files {
+		base := filepath.Base(file)
+		t.Run(base, func(t *testing.T) {
+			f, err := os.Open(file)
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer f.Close()
+			dec := json.NewDecoder(f)
+			var groups []testGroup
+			if err := dec.Decode(&groups); err != nil {
+				t.Fatal(err)
+			}
+			for _, g := range groups {
+				t.Run(g.Description, func(t *testing.T) {
+					rs, err := g.Schema.Resolve()
+					if err != nil {
+						t.Fatal(err)
+					}
+					for s := range g.Schema.all() {
+						if s.Defs != nil || s.Ref != "" {
+							t.Skip("schema or subschema has unimplemented keywords")
+						}
+					}
+					for _, test := range g.Tests {
+						t.Run(test.Description, func(t *testing.T) {
+							err = rs.Validate(test.Data)
+							if err != nil && test.Valid {
+								t.Errorf("wanted success, but failed with: %v", err)
+							}
+							if err == nil && !test.Valid {
+								t.Error("succeeded but wanted failure")
+							}
+							if t.Failed() {
+								t.Errorf("schema: %s", g.Schema.json())
+								t.Fatalf("instance: %v", test.Data)
+							}
+						})
+					}
+				})
+			}
+		})
+	}
+}