test: add some tests for Evaluator

app/src/test/java/net/youapps/calcyou/EvaluatorTest.kt

@@ -0,0 +1,62 @@
+package net.youapps.calcyou
+
+import net.youapps.calcyou.data.graphing.CompiledExpression
+import net.youapps.calcyou.data.graphing.Evaluator
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotNull
+import org.junit.Test
+import kotlin.math.abs
+import kotlin.math.cos
+import kotlin.math.exp
+import kotlin.math.ln
+import kotlin.math.log
+import kotlin.math.log10
+import kotlin.math.pow
+import kotlin.math.round
+import kotlin.math.sin
+import kotlin.math.sqrt
+import kotlin.math.tan
+import kotlin.random.Random
+
+internal class EvaluatorTest {
+
+    val testCases = mapOf(
+        "sin(x)" to { x: Double -> sin(x) },
+        "cos(x)" to { x: Double -> cos(x) },
+        "tan(x)" to { x: Double -> tan(x) },
+        "sqrt(x)" to { x: Double -> sqrt(x) },
+        "abs(x)" to { x: Double -> abs(x) },
+        "log(x)" to { x: Double -> ln(x) },
+        "exp(x)" to { x: Double -> exp(x) },
+        "log10(x)" to { x: Double -> log10(x) },
+        "log(x,2)" to { x: Double -> log(x, 2.0) },
+        "sin(x) + cos(x)" to { x: Double -> sin(x) + cos(x) },
+        "sin(x) * cos(x)" to { x: Double -> sin(x) * cos(x) },
+        "sin(x) / cos(x)" to { x: Double -> sin(x) / cos(x) },
+        "sin(x) - cos(x)" to { x: Double -> sin(x) - cos(x) },
+        "sin(x) ** 2" to { x: Double -> sin(x) * sin(x) },
+        "x * x" to { x: Double -> x * x },
+        "x ** 2" to { x: Double -> x.pow(2) },
+        "pow(x,3)" to { x: Double -> x.pow(3) },
+        "2" to { _: Double -> 2.0 },
+        "sqrt(4)" to { _: Double -> sqrt(4.0) },
+        "round(x)" to { x: Double -> round(x) },
+        "sin(2*PI)" to { _: Double -> sin(2 * Math.PI) },
+    )
+    val random = Random(System.currentTimeMillis())
+
+    @Test
+    fun `execute() should return correct answer for compiled expressions`() {
+        testCases.forEach { expression, func ->
+            val argument = random.nextDouble()
+            val compiled: CompiledExpression = Evaluator.compile(expression)
+
+            val answer = compiled.execute("x" to argument)
+
+            assertNotNull(answer)
+
+            val expected = func(argument)
+            assertEquals(expected, answer!!, 1e-6)
+        }
+    }
+}