Add test

src/main/kotlin/io/emeraldpay/dshackle/startup/configure/UpstreamCreator.kt

@@ -23,7 +23,9 @@ abstract class UpstreamCreator(
 
     companion object {
         fun getHash(nodeId: Int?, obj: Any, hashes: MutableMap<Short, Boolean>): Short =
-            nodeId?.toShort() ?: (obj.hashCode() % 65535).let {
+            nodeId?.toShort()?.also {
+                hashes[it] = true
+            } ?: (obj.hashCode() % 65535).let {
                 if (it == 0) 1 else it
             }.let { nonZeroHash ->
                 listOf<Function<Int, Int>>(

src/test/kotlin/io/emeraldpay/dshackle/startup/configure/UpstreamCreatorTest.kt

@@ -0,0 +1,38 @@
+package io.emeraldpay.dshackle.startup.configure
+
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.params.ParameterizedTest
+import org.junit.jupiter.params.provider.Arguments
+import org.junit.jupiter.params.provider.MethodSource
+
+class UpstreamCreatorTest {
+
+    @ParameterizedTest
+    @MethodSource("data")
+    fun `test getHash`(
+        inputHash: Int?,
+        obj: Any,
+        answer: Short
+    ) {
+        val hash = UpstreamCreator.getHash(inputHash, obj, hashes)
+
+        assertThat(hash).isEqualTo(answer)
+    }
+
+    companion object {
+        private val hashes: MutableMap<Short, Boolean> = HashMap()
+
+        @JvmStatic
+        fun data(): List<Arguments> =
+            listOf(
+                Arguments.of(49, 1, 49.toShort()),
+                Arguments.of(4000, 1, 4000.toShort()),
+                Arguments.of(24000, 1, 24000.toShort()),
+                Arguments.of(null, 49, (-49).toShort()),
+                Arguments.of(null, 49, (32718).toShort()),
+                Arguments.of(null, 49, (-32719).toShort()),
+                Arguments.of(null, 49, (-32768).toShort()),
+                Arguments.of(null, 49, (-32767).toShort())
+            )
+    }
+}