Add `SchemaVersion` type

js/modules/types/schema_version.js

@@ -0,0 +1,5 @@
+const isNumber = require('lodash/isNumber');
+
+
+exports.isValid = value =>
+  isNumber(value) && value >= 0;

test/modules/types/schema_version_test.js

@@ -0,0 +1,25 @@
+require('mocha-testcheck').install();
+const { assert } = require('chai');
+
+const SchemaVersion = require('../../../js/modules/types/schema_version');
+
+
+describe('SchemaVersion', () => {
+  describe('isValid', () => {
+    check.it(
+      'should return true for positive integers',
+      gen.posInt,
+      (input) => {
+        assert.isTrue(SchemaVersion.isValid(input));
+      }
+    );
+
+    check.it(
+      'should return false for any other value',
+      gen.primitive.suchThat(value => typeof value !== 'number' || value < 0),
+      (input) => {
+        assert.isFalse(SchemaVersion.isValid(input));
+      }
+    );
+  });
+});