Cleanup abstractions of "TestCase" class in unittest

tests/FactorGraphs/VariableTest.php

@@ -0,0 +1,22 @@
+<?php
+
+namespace DNW\Skills\Tests\FactorGraphs;
+
+use DNW\Skills\FactorGraphs\Variable;
+use DNW\Skills\Numerics\GaussianDistribution;
+use PHPUnit\Framework\TestCase;
+
+class VariableTest extends TestCase
+{
+    public function test(): void
+    {
+        $gd_prior = new GaussianDistribution();
+        $var = new Variable('dummy', $gd_prior);
+        $this->assertEquals($gd_prior, $var->getValue());
+        $gd_new = new GaussianDistribution();
+        $this->assertEquals($gd_new, $var->getValue());
+        $var->resetToPrior();
+        $this->assertEquals($gd_prior, $var->getValue());
+        $this->assertEquals('Variable[dummy]', (string)$var);
+    }
+}