Update tests to match current npm output

Author: deepy

src/test/groovy/com/github/gradle/node/SystemVersion_integTest.groovy

@@ -29,11 +29,11 @@ class SystemVersion_integTest extends AbstractIntegTest {
         result2.output.contains("Project repositories: 0")
 
         when:
-        def result3 = build(":npmHelp")
+        def result3 = build(":npmVersion")
 
         then:
-        result3.task(":npmHelp").outcome == TaskOutcome.SUCCESS
-        result3.output.contains("Usage: npm <command>")
+        result3.task(":npmVersion").outcome == TaskOutcome.SUCCESS
+        result3.output.contains("  npm: '")
 
         when:
         def result4 = build(":npxHelp")

src/test/groovy/com/github/gradle/node/npm/task/NpmInstall_integTest.groovy

@@ -118,7 +118,7 @@ class NpmInstall_integTest extends AbstractIntegTest {
         def result = buildAndFail('npmInstall')
 
         then:
-        result.output.contains('can only install packages with an existing package-lock.json')
+        result.output.contains('can only install with an existing package-lock.json')
         result.task(':npmInstall').outcome == TaskOutcome.FAILED
 
         when:

src/test/resources/fixtures/node-system-version/build.gradle

@@ -13,9 +13,8 @@ task countRepositories {
     }
 }
 
-task npmHelp(type: NpmTask) {
-    npmCommand = ["--help"]
-    ignoreExitValue = true
+task npmVersion(type: NpmTask) {
+    npmCommand = ["version"]
 }
 
 task npxHelp(type: NpxTask) {