### Question:
ToscaResourceInstaller { public String verifyTheFilePrefixInString(final String body, final String filenameToVerify) { String needlePrefix = "file: String prefixedFilenameToVerify = needlePrefix + filenameToVerify; if ((body == null) || (body.length() == 0) || (filenameToVerify == null) || (filenameToVerify.length() == 0)) { return body; } StringBuilder sb = new StringBuilder(body.length()); int currentIndex = 0; int startIndex = 0; while (currentIndex != -1) { startIndex = currentIndex; currentIndex = body.indexOf(prefixedFilenameToVerify, startIndex); if (currentIndex == -1) { break; } sb.append(body.substring(startIndex, currentIndex)); sb.append(filenameToVerify); currentIndex += prefixedFilenameToVerify.length(); } sb.append(body.substring(startIndex)); return sb.toString(); }  boolean isCsarAlreadyDeployed(ToscaResourceStructure toscaResourceStructure); boolean isResourceAlreadyDeployed(ResourceStructure vfResourceStruct, boolean serviceDeployed); void installTheComponentStatus(IStatusData iStatus); @Transactional(rollbackFor = {ArtifactInstallerException.class}) void installTheResource(ToscaResourceStructure toscaResourceStruct, ResourceStructure resourceStruct); @Transactional(rollbackFor = {ArtifactInstallerException.class}) void installTheVfResource(ToscaResourceStructure toscaResourceStruct, VfResourceStructure vfResourceStruct); void processWatchdog(String distributionId, String servideUUID, Optional<String> distributionNotification,
            String consumerId); String verifyTheFilePrefixInArtifacts(String filebody, VfResourceStructure vfResourceStructure,
            List<String> listTypes); String verifyTheFilePrefixInString(final String body, final String filenameToVerify); String getVnfcResourceInput(IEntityDetails vfcEntity, List<Input> inputList); List<IEntityDetails> getEntityDetails(ToscaResourceStructure toscaResourceStruct,
            EntityQueryBuilder entityType, TopologyTemplateQueryBuilder topologyTemplateBuilder, boolean nestedSearch); String getLeafPropertyValue(IEntityDetails entityDetails, String propName); @Transactional(rollbackFor = {ArtifactInstallerException.class}) void installNsstService(ToscaResourceStructure toscaResourceStruct, VfResourceStructure vfResourceStruct,
            String artifactContent);  }### Answer:
@Test public void verifyTheFilePrefixInStringTest() { String body = "abcabcabcfile: String filenameToVerify = "testfile.txt"; String expectedFileBody = "abcabcabctestfile.txtabcbabacbcabc"; String newFileBody = toscaInstaller.verifyTheFilePrefixInString(body, filenameToVerify); assertEquals(expectedFileBody, newFileBody); }
@Test public void verifyTheFilePrefixInStringNullBodyTest() { String body = null; String filenameToVerify = "testfile.txt"; String newFileBody = toscaInstaller.verifyTheFilePrefixInString(body, filenameToVerify); assertEquals(body, newFileBody); }
@Test public void verifyTheFilePrefixInStringEmptyBodyTest() { String body = ""; String filenameToVerify = "testfile.txt"; String newFileBody = toscaInstaller.verifyTheFilePrefixInString(body, filenameToVerify); assertEquals(body, newFileBody); }
@Test public void verifyTheFilePrefixInStringNullFilenameTest() { String body = "abcabcabcfile: String filenameToVerify = null; String newFileBody = toscaInstaller.verifyTheFilePrefixInString(body, filenameToVerify); assertEquals(body, newFileBody); }
@Test public void verifyTheFilePrefixInStringEmptyFilenameTest() { String body = "abcabcabcfile: String filenameToVerify = ""; String newFileBody = toscaInstaller.verifyTheFilePrefixInString(body, filenameToVerify); assertEquals(body, newFileBody); }