jest test fails with refs and Form

I have a search bar component which looks like:

  render () {
    const { onChangeTextInput } = this.props
    return (
      <Form
        name="searchForm"
        ref={(ref) => {
          this.searchForm = ref
        }}
      >
        <TextInput
          noSpacing
          placeholder={t('search')}
          name="search"
          validate="text"
          icon={this.icon}
          onChangeTextCallback={() => {
            onChangeTextInput(this.searchForm.values)
          }}
        />
        )
      </Form>
    )
  }
}

I am using a shallow render and jest to run a unit test to test the following scenario"

1. User types a character in text input
2. a callback method gets fired which provides the user with the text as an argument.

The test I am running is stated as:

 test('SearchBar returns value on text change', () => {
        const onChangeFunction = jest.fn()
        const obj = shallow(
          <SearchBar onChangeTextInput={onChangeFunction} />
        )
        obj.find('TextInput').props().onChangeTextCallback('h')
        expect(onChangeFunction).toHaveBeenCalledWith('h')
      })

I getting a weird error stating :

TypeError: Cannot read property 'values' of undefined

  51 |           icon={this.icon}
  52 |           onChangeTextCallback={() => {
> 53 |             onChangeTextInput(this.searchForm.values)
     |                                                 ^
  54 |           }}
  55 |         />
  56 |         )

My obj.html() dump for the test looks like:

<Form name="searchForm" if={true}>
  <TextInput
    noSpacing={true}
    placeholder="search"
    name="search"
    validate="text"
    icon={{
      $$typeof: Symbol(react.element),
      type: [(Function: Icon)],
      key: null,
      ref: null,
      props: {
        name: "search",
        size: 25,
        color: "#00a8ca",
        style: { position: "absolute", right: 0, bottom: 7 },
        allowFontScaling: false,
        type: "MaterialIcons",
        if: true,
      },
      _owner: null,
      _store: {},
    }}
    onChangeTextCallback={[(Function: onChangeTextCallback)]}
    value={null}
    style={{}}
    hasFloatingLabel={true}
    numberOfLines={1}
    isPassword={false}
    if={true}
  />
  )
</Form>

what is happening here? I have custom form that gives me values through refs. Do I need to do something and maybe initialize the Form component? please help, I am relatively new to this stuff.