✅ Add tests to Interpolator

app/src/main/kotlin/br/com/colman/petals/withdrawal/interpolator/Interpolator.kt

@@ -6,7 +6,6 @@ import org.apache.commons.math3.analysis.interpolation.UnivariateInterpolator
 import org.apache.commons.math3.analysis.polynomials.PolynomialSplineFunction
 import java.time.Duration
 
-// TODO Add tests
 class Interpolator(
   val data: Map<Duration, Double>
 ) : UnivariateInterpolator, UnivariateFunction {
@@ -21,10 +20,4 @@ class Interpolator(
   override fun interpolate(xs: DoubleArray?, ys: DoubleArray?): UnivariateFunction = dataInterpolator
 
   override fun value(x: Double): Double = dataInterpolator.value(x.coerceAtMost(maxPossibleX.toDouble()))
-
-  fun calculatePercentage(secondsQuit: Long): Double {
-    val maxValue = data.values.max()
-    val currentValue = value(secondsQuit.coerceAtMost(maxPossibleX).toDouble())
-    return currentValue / maxValue
-  }
 }

app/src/test/kotlin/br/com/colman/petals/withdrawal/interpolator/InterpolatorTest.kt

@@ -0,0 +1,46 @@
+package br.com.colman.petals.withdrawal.interpolator
+
+import io.kotest.core.spec.style.FunSpec
+import io.kotest.matchers.shouldBe
+import org.apache.commons.math3.analysis.UnivariateFunction
+import java.time.Duration.ofSeconds as seconds
+
+class InterpolatorTest : FunSpec({
+
+  test("Should respect maxPossibleX") {
+    val data = mapOf(
+      seconds(0) to 0.0,
+      seconds(5) to 10.0,
+      seconds(10) to 20.0
+    )
+    val target = Interpolator(data)
+
+    target.value(10.0) shouldBe 20.0
+    target.value(100.0) shouldBe 20.0
+  }
+
+  test("should implement UnivariateFunction") {
+    val data = mapOf(
+      seconds(0) to 0.0,
+      seconds(2) to 4.0
+    )
+    val target = Interpolator(data)
+
+    target.value(1.0) shouldBe 2.0
+  }
+
+  test("should interpolate ignoring given arrays") {
+    val data = mapOf(
+      seconds(0) to 0.0,
+      seconds(10) to 10.0
+    )
+
+    val interpolator = Interpolator(data)
+    val univariateFunction: UnivariateFunction = interpolator.interpolate(
+      doubleArrayOf(),
+      doubleArrayOf()
+    )
+
+    univariateFunction.value(5.0) shouldBe 5.0
+  }
+})