A system to detect errors in digital assistant-based applications, comprising: a data processing system comprising one or more processors to: identify an application package file for an application, provided by an application developer, that interfaces with a digital assistant via audio signals; receive, from a device of the application developer, a transcript file for the application; establish, in a web browser executed by the device of the application developer, a first iframe of a simulator component for digital assistant-based applications, the simulator component to establish a plurality of iframes within the first iframe that communicate between the plurality of iframes via a two-way communication protocol; provide, for display in the web browser executed by the device of the application developer, a second iframe within the first iframe to load a control setting for the simulator component; provide, for display in the web browser, a third iframe within the first iframe to display output of the simulator component; provide, for display in the web browser, a fourth iframe within the first iframe to execute a state machine to generate a query based on the transcript file and responsive to the control setting established in the second iframe; the simulator component to: provide, via the fourth iframe, the query for display via the web browser; receive, responsive to the query, an input; update a state of the state machine responsive to the query and the input to generate an application output for display via the third iframe; identify, based on a second query generated by the state machine responsive to the input, an error with the application; and terminate, responsive to the error, at least one of the plurality of iframes established by the simulator component. identify an application package file for an application, provided by an application developer, that interfaces with a digital assistant via audio signals; receive, from a device of the application developer, a transcript file for the application; establish, in a web browser executed by the device of the application developer, a first iframe of a simulator component for digital assistant-based applications, the simulator component to establish a plurality of iframes within the first iframe that communicate between the plurality of iframes via a two-way communication protocol; provide, for display in the web browser executed by the device of the application developer, a second iframe within the first iframe to load a control setting for the simulator component; provide, for display in the web browser, a third iframe within the first iframe to display output of the simulator component; provide, for display in the web browser, a fourth iframe within the first iframe to execute a state machine to generate a query based on the transcript file and responsive to the control setting established in the second iframe; the simulator component to: provide, via the fourth iframe, the query for display via the web browser; receive, responsive to the query, an input; update a state of the state machine responsive to the query and the input to generate an application output for display via the third iframe; identify, based on a second query generated by the state machine responsive to the input, an error with the application; and terminate, responsive to the error, at least one of the plurality of iframes established by the simulator component. provide, via the fourth iframe, the query for display via the web browser; receive, responsive to the query, an input; update a state of the state machine responsive to the query and the input to generate an application output for display via the third iframe; identify, based on a second query generated by the state machine responsive to the input, an error with the application; and terminate, responsive to the error, at least one of the plurality of iframes established by the simulator component.