Add test support for intrinsic sized nodes

Summary: This diff adds support for intrinsic sizing in generated tests. This is done by importing a testing font called "Ahem" which, as used, has an exact width and height of 10px for each character. Support has been added for C++, Java, and Javascript generated tests.

Differential Revision: D58307002

gentest/gentest-java.js

@@ -55,6 +55,7 @@ JavaEmitter.prototype = Object.create(Emitter.prototype, {
         'import org.junit.Test;',
         'import org.junit.runner.RunWith;',
         'import org.junit.runners.Parameterized;',
+        'import com.facebook.yoga.utils.TestUtils;',
         '',
         '@RunWith(Parameterized.class)',
         'public class YogaTest {',
@@ -465,4 +466,13 @@ JavaEmitter.prototype = Object.create(Emitter.prototype, {
       );
     },
   },
+
+  YGNodeSetMeasureFunc: {
+    value: function (nodeName, innerText) {
+      this.push(`${nodeName}.setData("${innerText}");`);
+      this.push(
+        `${nodeName}.setMeasureFunction(new TestUtils.intrinsicMeasureFunction());`,
+      );
+    },
+  },
 });