当我的单元测试运行具有合同的方法<>，它与一个错误而失败：
An exception occurred while invoking executor 'executor://mswptestadapter/v1': Object reference not set to an instance of an object.
========== Run test finished: 0 run (0:00:28.8388006) ==========
这里是pxproj文件合同设置。
<CodeContractsEnableRuntimeChecking>False</CodeContractsEnableRuntimeChecking>
<CodeContractsRuntimeOnlyPublicSurface>False</CodeContractsRuntimeOnlyPublicSurface>
<CodeContractsRuntimeThrowOnFailure>True</CodeContractsRuntimeThrowOnFailure>
<CodeContractsRuntimeCallSiteRequires>False</CodeContractsRuntimeCallSiteRequires>
<CodeContractsRuntimeSkipQuantifiers>False</CodeContractsRuntimeSkipQuantifiers>
<CodeContractsRunCodeAnalysis>False</CodeContractsRunCodeAnalysis>
<CodeContractsNonNullObligations>True</CodeContractsNonNullObligations>
<CodeContractsBoundsObligations>True</CodeContractsBoundsObligations>
<CodeContractsArithmeticObligations>False</CodeContractsArithmeticObligations>
<CodeContractsEnumObligations>False</CodeContractsEnumObligations>
<CodeContractsRedundantAssumptions>False</CodeContractsRedundantAssumptions>
<CodeContractsMissingPublicRequiresAsWarnings>True</CodeContractsMissingPublicRequiresAsWarnings>
<CodeContractsInferRequires>True</CodeContractsInferRequires>
<CodeContractsInferEnsures>False</CodeContractsInferEnsures>
<CodeContractsInferObjectInvariants>False</CodeContractsInferObjectInvariants>
<CodeContractsSuggestAssumptions>False</CodeContractsSuggestAssumptions>
<CodeContractsSuggestRequires>True</CodeContractsSuggestRequires>
<CodeContractsSuggestObjectInvariants>False</CodeContractsSuggestObjectInvariants>
<CodeContractsRunInBackground>True</CodeContractsRunInBackground>
<CodeContractsShowSquigglies>True</CodeContractsShowSquigglies>
<CodeContractsUseBaseLine>False</CodeContractsUseBaseLine>
<CodeContractsEmitXMLDocs>False</CodeContractsEmitXMLDocs>
<CodeContractsCustomRewriterAssembly />
<CodeContractsCustomRewriterClass />
<CodeContractsLibPaths />
<CodeContractsExtraRewriteOptions />
<CodeContractsExtraAnalysisOptions />
<CodeContractsSQLServerOption />
<CodeContractsBaseLineFile />
<CodeContractsCacheAnalysisResults>True</CodeContractsCacheAnalysisResults>
<CodeContractsFailBuildOnWarnings>False</CodeContractsFailBuildOnWarnings>
<CodeContractsRuntimeCheckingLevel>Full</CodeContractsRuntimeCheckingLevel>
<CodeContractsReferenceAssembly>%28none%29</CodeContractsReferenceAssembly>
<CodeContractsAnalysisWarningLevel>0</CodeContractsAnalysisWarningLevel>
