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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019d0c47-5399-7f98-bc65-3e06e7c0076f,g:86f01b67-2c3a-4583-8795-a8047fbdba5b-->
<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-20260504.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_019d0c47-5399-76d9-bac2-40c5a4528632" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_019d0c47-5399-7461-bdb7-687e7bdd22cb" 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_019d0c47-5399-76d9-bac2-40c5a4528632" xlink:to="loc_dei_DocumentInformationTable_019d0c47-5399-7461-bdb7-687e7bdd22cb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019d0c47-5399-715e-828e-ea18cb2e3d7e" 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_019d0c47-5399-7461-bdb7-687e7bdd22cb" xlink:to="loc_dei_LegalEntityAxis_019d0c47-5399-715e-828e-ea18cb2e3d7e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019d0c47-5399-715e-828e-ea18cb2e3d7e_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_019d0c47-5399-715e-828e-ea18cb2e3d7e" xlink:to="loc_dei_EntityDomain_019d0c47-5399-715e-828e-ea18cb2e3d7e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019d0c47-5399-7d0d-922b-460261810d5e" 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_019d0c47-5399-715e-828e-ea18cb2e3d7e" xlink:to="loc_dei_EntityDomain_019d0c47-5399-7d0d-922b-460261810d5e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_019d0c47-5399-7312-b07c-48c0c274faa4" 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_019d0c47-5399-76d9-bac2-40c5a4528632" xlink:to="loc_dei_EntityRegistrantName_019d0c47-5399-7312-b07c-48c0c274faa4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_019d0c47-5399-7e7a-8673-331da1e3e9b7" 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_019d0c47-5399-76d9-bac2-40c5a4528632" xlink:to="loc_dei_DocumentType_019d0c47-5399-7e7a-8673-331da1e3e9b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_019d0c47-5399-7976-bcba-6fbc20a8f74b" 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_019d0c47-5399-76d9-bac2-40c5a4528632" xlink:to="loc_dei_DocumentPeriodEndDate_019d0c47-5399-7976-bcba-6fbc20a8f74b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_019d0c47-5399-7baa-ad1b-72350b5ee27d" 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_019d0c47-5399-76d9-bac2-40c5a4528632" xlink:to="loc_dei_EntityIncorporationStateCountryCode_019d0c47-5399-7baa-ad1b-72350b5ee27d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_019d0c47-5399-7a4f-aaa7-08912622a38b" 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_019d0c47-5399-76d9-bac2-40c5a4528632" xlink:to="loc_dei_EntityFileNumber_019d0c47-5399-7a4f-aaa7-08912622a38b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_019d0c47-5399-754a-a818-96c8d7cbaf4d" 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_019d0c47-5399-76d9-bac2-40c5a4528632" xlink:to="loc_dei_EntityTaxIdentificationNumber_019d0c47-5399-754a-a818-96c8d7cbaf4d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_019d0c47-5399-7c47-b1f5-ed434f1ff19a" 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_019d0c47-5399-76d9-bac2-40c5a4528632" xlink:to="loc_dei_EntityAddressAddressLine1_019d0c47-5399-7c47-b1f5-ed434f1ff19a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine2_019d0c47-5399-724b-9e58-58f7935e2ab4" 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_019d0c47-5399-76d9-bac2-40c5a4528632" xlink:to="loc_dei_EntityAddressAddressLine2_019d0c47-5399-724b-9e58-58f7935e2ab4" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_019d0c47-5399-7238-8fb6-c7236eb743cc" 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_019d0c47-5399-76d9-bac2-40c5a4528632" xlink:to="loc_dei_EntityAddressCityOrTown_019d0c47-5399-7238-8fb6-c7236eb743cc" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_019d0c47-5399-7d6c-9eb8-8db83e147774" 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_019d0c47-5399-76d9-bac2-40c5a4528632" xlink:to="loc_dei_EntityAddressStateOrProvince_019d0c47-5399-7d6c-9eb8-8db83e147774" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_019d0c47-5399-79fc-bf2a-a8cd6b8de065" 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_019d0c47-5399-76d9-bac2-40c5a4528632" xlink:to="loc_dei_EntityAddressPostalZipCode_019d0c47-5399-79fc-bf2a-a8cd6b8de065" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_019d0c47-5399-7ff9-a636-bd2453112b2b" 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_019d0c47-5399-76d9-bac2-40c5a4528632" xlink:to="loc_dei_CityAreaCode_019d0c47-5399-7ff9-a636-bd2453112b2b" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_019d0c47-5399-765c-be5e-95805d39de67" 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_019d0c47-5399-76d9-bac2-40c5a4528632" xlink:to="loc_dei_LocalPhoneNumber_019d0c47-5399-765c-be5e-95805d39de67" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_WrittenCommunications_019d0c47-5399-7d46-b017-1997bc139f72" 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_019d0c47-5399-76d9-bac2-40c5a4528632" xlink:to="loc_dei_WrittenCommunications_019d0c47-5399-7d46-b017-1997bc139f72" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SolicitingMaterial_019d0c47-5399-78bb-b1e6-782f7a1db88b" 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_019d0c47-5399-76d9-bac2-40c5a4528632" xlink:to="loc_dei_SolicitingMaterial_019d0c47-5399-78bb-b1e6-782f7a1db88b" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementTenderOffer_019d0c47-5399-7ce3-9c2f-9a396fe46fc1" 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_019d0c47-5399-76d9-bac2-40c5a4528632" xlink:to="loc_dei_PreCommencementTenderOffer_019d0c47-5399-7ce3-9c2f-9a396fe46fc1" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementIssuerTenderOffer_019d0c47-5399-7359-8bb0-113d24d67382" 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_019d0c47-5399-76d9-bac2-40c5a4528632" xlink:to="loc_dei_PreCommencementIssuerTenderOffer_019d0c47-5399-7359-8bb0-113d24d67382" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_019d0c47-5399-7086-abaf-a18687924a33" 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_019d0c47-5399-76d9-bac2-40c5a4528632" xlink:to="loc_dei_Security12bTitle_019d0c47-5399-7086-abaf-a18687924a33" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_019d0c47-5399-7077-be85-004c09f6df3f" 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_019d0c47-5399-76d9-bac2-40c5a4528632" xlink:to="loc_dei_TradingSymbol_019d0c47-5399-7077-be85-004c09f6df3f" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_019d0c47-5399-7cfc-9968-1bd58d7c914a" 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_019d0c47-5399-76d9-bac2-40c5a4528632" xlink:to="loc_dei_SecurityExchangeName_019d0c47-5399-7cfc-9968-1bd58d7c914a" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_019d0c47-5399-782b-b8d6-3a88c516eec7" 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_019d0c47-5399-76d9-bac2-40c5a4528632" xlink:to="loc_dei_EntityEmergingGrowthCompany_019d0c47-5399-782b-b8d6-3a88c516eec7" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_019d0c47-5399-76d2-b67e-fede483a1426" 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_019d0c47-5399-76d9-bac2-40c5a4528632" xlink:to="loc_dei_AmendmentFlag_019d0c47-5399-76d2-b67e-fede483a1426" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_019d0c47-5399-7ad2-a025-704176a65259" 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_019d0c47-5399-76d9-bac2-40c5a4528632" xlink:to="loc_dei_EntityCentralIndexKey_019d0c47-5399-7ad2-a025-704176a65259" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_019d0c47-5399-7ab8-ae6d-83c25fd4a786" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_AmendmentFlag"/>
  </link:definitionLink>
</link:linkbase>
