test: add more unit tests for checks (#58)

Author: smyrick

src/main/kotlin/com/expedia/graphql/schema/exceptions/InvalidSchemaException.kt

@@ -3,4 +3,4 @@ package com.expedia.graphql.schema.exceptions
 /**
  * Exception thrown on schema creation if no queries and no mutations are specified.
  */
-class InvalidSchemaException : GraphQLKotlinException("Schema requires at least one query or mutation")
+class InvalidSchemaException : GraphQLKotlinException("Schema requires at least one query")

src/main/kotlin/com/expedia/graphql/toSchema.kt

@@ -17,7 +17,7 @@ fun toSchema(
     mutations: List<TopLevelObjectDef> = emptyList(),
     config: SchemaGeneratorConfig
 ): GraphQLSchema {
-    if (queries.isEmpty() && mutations.isEmpty()) {
+    if (queries.isEmpty()) {
         throw InvalidSchemaException()
     }
     return SchemaGenerator(queries, mutations, config).generate()

src/test/kotlin/com/expedia/graphql/schema/generator/SchemaGeneratorTest.kt

@@ -18,6 +18,7 @@ import java.net.CookieManager
 import java.util.UUID
 import kotlin.test.Test
 import kotlin.test.assertEquals
+import kotlin.test.assertFailsWith
 import kotlin.test.assertNotNull
 import kotlin.test.assertTrue
 
@@ -38,6 +39,17 @@ class SchemaGeneratorTest {
         assertEquals(1, geo?.get("query")?.get("id"))
     }
 
+    @Test
+    fun `SchemaGenerator throws exception on a mutation only schema`() {
+        assertFailsWith(InvalidSchemaException::class) {
+            toSchema(
+                emptyList(),
+                listOf(TopLevelObjectDef(MutationObject())),
+                config = testSchemaConfig
+            )
+        }
+    }
+
     @Test
     fun `Schema generator exposes arrays of primitive types as function arguments`() {
         val schema = toSchema(listOf(TopLevelObjectDef(QueryWithArray())), config = testSchemaConfig)