diff --git a/Taskfile.yml b/Taskfile.yml
index 4fadb79..acc2368 100644
--- a/Taskfile.yml
+++ b/Taskfile.yml
@@ -25,3 +25,7 @@ tasks:
                     -c ajv-keywords \
                     -s schemas-yaml/character.yml \
                     -d {{.CLI_ARGS}}
+    test:
+        deps: [ schemas ]
+        cmds:
+            - vitest run
diff --git a/package.json b/package.json
index 639e1e3..85d65d1 100644
--- a/package.json
+++ b/package.json
@@ -15,9 +15,11 @@
   "author": "Yanick Champoux <yanick@babyl.ca> (http://techblog.babyl.ca/)",
   "license": "ISC",
   "devDependencies": {
-    "prettier": "^2.6.2"
+    "prettier": "^2.6.2",
+    "vitest": "^0.10.0"
   },
   "dependencies": {
+    "ajv": "^8.11.0",
     "ajv-cli": "^5.0.0",
     "ajv-keywords": "^5.1.0"
   }
diff --git a/schemas-json/character.json b/schemas-json/character.json
new file mode 100644
index 0000000..f97c88f
--- /dev/null
+++ b/schemas-json/character.json
@@ -0,0 +1,50 @@
+{
+   "$defs" : {
+      "statistic" : {
+         "maximum" : 20,
+         "minimum" : 1,
+         "type" : "number"
+      }
+   },
+   "$id" : "https://hyperboria.babyl.ca/character.json",
+   "additionalProperties" : false,
+   "properties" : {
+      "name" : {
+         "type" : "string"
+      },
+      "player" : {
+         "type" : "string"
+      },
+      "statistics" : {
+         "allRequired" : true,
+         "properties" : {
+            "charisma" : {
+               "$ref" : "#/$defs/statistic"
+            },
+            "constitution" : {
+               "$ref" : "#/$defs/statistic"
+            },
+            "dexterity" : {
+               "$ref" : "#/$defs/statistic"
+            },
+            "intelligence" : {
+               "$ref" : "#/$defs/statistic"
+            },
+            "strength" : {
+               "$ref" : "#/$defs/statistic"
+            },
+            "wisdom" : {
+               "$ref" : "#/$defs/statistic"
+            }
+         },
+         "type" : "object"
+      }
+   },
+   "required" : [
+      "name",
+      "player",
+      "statistics"
+   ],
+   "title" : "Hyperboria character sheet",
+   "type" : "object"
+}
diff --git a/src/statistics.test.js b/src/statistics.test.js
new file mode 100644
index 0000000..42efb1f
--- /dev/null
+++ b/src/statistics.test.js
@@ -0,0 +1,20 @@
+import { test, expect } from "vitest";
+
+import Ajv from "ajv";
+
+import characterSchema from "../schemas-json/character.json";
+
+const ajv = new Ajv();
+const validate = ajv.compile(characterSchema.$defs.statistic);
+
+test("good statistic", () => {
+    expect(validate(12)).toBeTruthy();
+    expect(validate.errors).toBeNull();
+});
+
+test("bad statistic", () => {
+    expect(validate(21)).toBeFalsy();
+    expect(validate.errors[0]).toMatchObject({
+        message: "must be <= 20",
+    });
+});