<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:01a015bd-a169-7da5-a6f8-09c97b8e5af5,g:79886d47-eaae-4fa0-ad09-3b5ccf829aa0-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.intt.com/role/DocumentAndEntityInformation" xlink:type="simple" xlink:href="intt-20261106.xsd#DocumentAndEntityInformation"/>
  <link:definitionLink xlink:role="http://www.intt.com/role/DocumentAndEntityInformation" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_01a015bd-a169-7554-97a1-a4b2548af123" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_01a015bd-a169-75f3-9f69-49af1bc58312" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_01a015bd-a169-7554-97a1-a4b2548af123" xlink:to="loc_dei_DocumentInformationTable_01a015bd-a169-75f3-9f69-49af1bc58312" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_01a015bd-a169-7f70-b55f-7b5094e84152" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_01a015bd-a169-75f3-9f69-49af1bc58312" xlink:to="loc_dei_LegalEntityAxis_01a015bd-a169-7f70-b55f-7b5094e84152" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_01a015bd-a169-7f70-b55f-7b5094e84152_default" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_01a015bd-a169-7f70-b55f-7b5094e84152" xlink:to="loc_dei_EntityDomain_01a015bd-a169-7f70-b55f-7b5094e84152_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_01a015bd-a169-75ea-9da3-aff72a169231" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_01a015bd-a169-7f70-b55f-7b5094e84152" xlink:to="loc_dei_EntityDomain_01a015bd-a169-75ea-9da3-aff72a169231" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_01a015bd-a169-7e4d-9c30-3f81cd6f15b3" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a015bd-a169-7554-97a1-a4b2548af123" xlink:to="loc_dei_EntityRegistrantName_01a015bd-a169-7e4d-9c30-3f81cd6f15b3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_01a015bd-a169-708e-9860-118160dbbdac" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a015bd-a169-7554-97a1-a4b2548af123" xlink:to="loc_dei_DocumentType_01a015bd-a169-708e-9860-118160dbbdac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_01a015bd-a169-7a7a-ab3a-21e8347e8826" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a015bd-a169-7554-97a1-a4b2548af123" xlink:to="loc_dei_DocumentPeriodEndDate_01a015bd-a169-7a7a-ab3a-21e8347e8826" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_01a015bd-a169-72e3-9516-01078e036674" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a015bd-a169-7554-97a1-a4b2548af123" xlink:to="loc_dei_EntityIncorporationStateCountryCode_01a015bd-a169-72e3-9516-01078e036674" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_01a015bd-a169-7c88-b3c2-304de831e2d7" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a015bd-a169-7554-97a1-a4b2548af123" xlink:to="loc_dei_EntityFileNumber_01a015bd-a169-7c88-b3c2-304de831e2d7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_01a015bd-a169-71df-9f4c-e16965eb9573" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a015bd-a169-7554-97a1-a4b2548af123" xlink:to="loc_dei_EntityTaxIdentificationNumber_01a015bd-a169-71df-9f4c-e16965eb9573" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_01a015bd-a169-7751-ba61-528221209d64" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a015bd-a169-7554-97a1-a4b2548af123" xlink:to="loc_dei_EntityAddressAddressLine1_01a015bd-a169-7751-ba61-528221209d64" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine2_01a015bd-a169-7d2f-bb32-a24eb462fa02" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressAddressLine2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a015bd-a169-7554-97a1-a4b2548af123" xlink:to="loc_dei_EntityAddressAddressLine2_01a015bd-a169-7d2f-bb32-a24eb462fa02" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_01a015bd-a169-73a9-92b6-c1081183548d" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a015bd-a169-7554-97a1-a4b2548af123" xlink:to="loc_dei_EntityAddressCityOrTown_01a015bd-a169-73a9-92b6-c1081183548d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_01a015bd-a169-735c-8c53-074bf393cb1c" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a015bd-a169-7554-97a1-a4b2548af123" xlink:to="loc_dei_EntityAddressStateOrProvince_01a015bd-a169-735c-8c53-074bf393cb1c" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_01a015bd-a169-7fcf-9a04-ed42dfba13e5" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a015bd-a169-7554-97a1-a4b2548af123" xlink:to="loc_dei_EntityAddressPostalZipCode_01a015bd-a169-7fcf-9a04-ed42dfba13e5" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_01a015bd-a169-7fc6-8070-78b43307131f" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a015bd-a169-7554-97a1-a4b2548af123" xlink:to="loc_dei_CityAreaCode_01a015bd-a169-7fc6-8070-78b43307131f" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_01a015bd-a169-70d5-97d1-7e48fbe885cc" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a015bd-a169-7554-97a1-a4b2548af123" xlink:to="loc_dei_LocalPhoneNumber_01a015bd-a169-70d5-97d1-7e48fbe885cc" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_WrittenCommunications_01a015bd-a169-7fc9-8549-6c4ef025a922" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_WrittenCommunications"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a015bd-a169-7554-97a1-a4b2548af123" xlink:to="loc_dei_WrittenCommunications_01a015bd-a169-7fc9-8549-6c4ef025a922" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SolicitingMaterial_01a015bd-a169-7f9b-9a12-ad70701e5405" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_SolicitingMaterial"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a015bd-a169-7554-97a1-a4b2548af123" xlink:to="loc_dei_SolicitingMaterial_01a015bd-a169-7f9b-9a12-ad70701e5405" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementTenderOffer_01a015bd-a169-7174-b112-67dad1eb5e75" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_PreCommencementTenderOffer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a015bd-a169-7554-97a1-a4b2548af123" xlink:to="loc_dei_PreCommencementTenderOffer_01a015bd-a169-7174-b112-67dad1eb5e75" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementIssuerTenderOffer_01a015bd-a169-7ccd-94f6-51c0e7f20c9d" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_PreCommencementIssuerTenderOffer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a015bd-a169-7554-97a1-a4b2548af123" xlink:to="loc_dei_PreCommencementIssuerTenderOffer_01a015bd-a169-7ccd-94f6-51c0e7f20c9d" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_01a015bd-a169-7e44-9ce8-7ecca3866f05" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a015bd-a169-7554-97a1-a4b2548af123" xlink:to="loc_dei_Security12bTitle_01a015bd-a169-7e44-9ce8-7ecca3866f05" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_01a015bd-a169-734b-ab86-cde7e3e31f4d" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a015bd-a169-7554-97a1-a4b2548af123" xlink:to="loc_dei_TradingSymbol_01a015bd-a169-734b-ab86-cde7e3e31f4d" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_01a015bd-a169-742a-9528-8677c639c76c" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a015bd-a169-7554-97a1-a4b2548af123" xlink:to="loc_dei_SecurityExchangeName_01a015bd-a169-742a-9528-8677c639c76c" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_01a015bd-a169-7aae-aaf5-164be3565fc0" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a015bd-a169-7554-97a1-a4b2548af123" xlink:to="loc_dei_EntityEmergingGrowthCompany_01a015bd-a169-7aae-aaf5-164be3565fc0" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_01a015bd-a169-7c6e-a46e-b6c84a1c84d5" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a015bd-a169-7554-97a1-a4b2548af123" xlink:to="loc_dei_AmendmentFlag_01a015bd-a169-7c6e-a46e-b6c84a1c84d5" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_01a015bd-a169-7e31-b084-d6671bb26975" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a015bd-a169-7554-97a1-a4b2548af123" xlink:to="loc_dei_EntityCentralIndexKey_01a015bd-a169-7e31-b084-d6671bb26975" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_01a015bd-a169-7a5e-b5a0-7b3d6a41f8a3" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_AmendmentFlag"/>
  </link:definitionLink>
</link:linkbase>
