Navlang - DSL for automatically navigating around inside web applications using visual analysis

Table of Contents


Any lines starting with # (or spaces followed by #) are treated as code comments and will be discarded by the compiler. For example:

# this is a comment
    # so is this line...

Comments must be on its own lines according to the current implementation.

We also support the block comment syntax, #{ ... }, which can span multiple lines, as in

    This is a

You can specify double or tripple curly brackets to disambiguate special cases where the } character is used in the contents being commented out via the block comment syntax, as in

    This is a block comment
    containing #{ ... }

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Each navlang program usually specifies one or more sections to declare how the current web page should look like and how to locate the page elements accurately for various operations.

Unlike traditional Web UI end-to-end (e2e) testing techniques, we never use CSS selectors or XPath queries to locate page elements, but just use visual information. It is always a shame to require test writers to check out the HTML source code or inspect an element via web browsers' developer tools to write any test scripts.

All the section values must take at least one level of indentation.

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This section specifies the qualitative visual layout of the interested web page elements as well as their notable neighbors.

Each page element is enclosed in a pair of square brackets ([]) and has the following format:

[Type Label]=ID

or just

[Type Label]

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Available element types

The Type part can take one of the following values

  • Textbox
  • Link
  • Button
  • Label
  • Title
  • Text
  • Checkbox
  • Radio
  • Toggle
  • Dropdown
  • Option
  • File
  • CodeMirror

And the Label part specifies the pattern for the string label associated with the element. Right now, only literal string patterns are supported, as in

[Textbox "User Name"]

[Link 'Delete']
[Title /[a-z]\d+/]

The following escaping sequences are allowed in the double-quoted or single-quoted literal strings:


The regex patterns are always anchored, meaning for /xxx/ on the navlang land, the JavaScript regex construct /^(?:xxx)$/i will be used on the JavaScript land.

The label can be empty string, [Textbox ""] meaning that Textbox with no label will match it.

The label can also be empty regex //, [Textbox //] meaning that Textbox may or may not have the label.

The =ID part defines an ID for the current page element, which can be used to reference the same page element in the subsequent commands, as in

    [Button "Create User"]=create

click -> create   # click on the element of the ID "create"

The =ID specifier is optional and be omitted when no later references are needed.

If an element is specified with an ID, it can be referenced in the next elems block using [=ID]. For example, to select an option in a dropdown list:

    [Dropdown "Please select action type"]=select-action

click -> select-action

    [Option "Redirect"]=redirect

click -> redirect

Please be careful, we use some words as "Reserved words" and they cannot be used for element ids. Currently, they are

  • stdout
  • stderr
  • status
  • and the words above with a number suffix, like stdout1, stderr2, etc. We use them to store the results of multiple commands.

The elems label can also takes quantifiers like (?). For example, the following section allows the element pattern layout match to fail:

    [Title   "Domain"] [Title "Label"]
    [Link ""] [Label "Test application"]   [Link "Delete"]=delete

    click -> delete

In this example, only when the link is found with its specified neighbors, it clicks on the element link with the ID delete.

Basically, elems(?) can be used with the found and not-found label sections to do branching.

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Currently we will take a <label> as a Toggle when:

  1. It contains or points to a hidden <input type="checkbox">
  2. It must display as a block
  3. It must do not have brothers with same height

And the label in [Toggle "some toggle"] will be compared with <input type="checkbox">'s name.

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Currently we will take a <textarea> + <div> as a CodeMirror when:

  1. <textarea> is hidden
  2. <div> is visible and has the class '.CodeMirror'

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Negation of elements

We can add the ! prefix operator to each element to assert that this element should not exist on the page. For example,

    ![Textbox "Name"]

This would fail to match when the Textbox element with the label Name does exist on the current page.

Context-sensitive negation support is still a TODO.

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This section is usually used with an earlier elems(?) section to specify commands in the fall through branch (i.e., when the elems(?) actually matches the elements.

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This section is usually used with an earlier elems(?) section to specify commands in the jump-out branch (i.e., when the elems(?) does not match anything).

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This section is used to embed markdown descriptions with screenshots when --gen-doc option is specified. For example, consider this sample.nav file:

goto URL
    Here is the home site of **Some Thing**.

To generate the document, we first compile it using --gen-doc like:

./navlang --gen-doc sample.nav

The window size of the Chromium can be set by using ---window-size like:

./navlang --gen-doc --window-size=1200x800 sample.nav

The default window size is 800x600 pixels. You can also use the environment variable NAVLANG_WINDOW_SIZE to configure it.

Then run the output JavaScript file, node sample.js, we will get the markdown file The markdown output is like this:

Here is the home site of **Some Thing**.

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To generate HTML file

If you want to generate HTML file from markdown file, you need to install marked by npm install marked. Then use the script gen-html.js like this:

$ node gen-html.js
sample.html is ready.

It will output the html file with github style. Here is an example:

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This section specifies the relative location on a whole web page for the element layout specification in a subsequent elems section. We use the X mark for the placeholder for the positions hold by an interested page element, while using - to identify the uninterested background space. Below is an example:


    [Title "Login"]
    [Textbox "User Name"]=user
    [Textbox "Password"]=pass
    [Checkbox "Remember Me"]=remem
    [Button "Login"]=login

This indicates that the element group specified under the elems section should be on the left hand side part of the whole page.

The loc section is optional and can be omitted.

Note: the loc section has not yet been fully implemented.

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Executes commands via shell. One line at a time, unless ending with \. Normal output will go to stdout, warnings and errors will go to stderr. You can check them through åthese variables.

After all commands are executed, you can check the result like this:

    echo 'hello'

stdout is 'hello'
stdout eq 'hello'
# here, `is` has the same feature with `eq`

or check stderr output like this:


stderr contains /helloworld:( command)? not found/
status eq '127'
# error message contains the line number and file name, so it is better to use
# a regexp matching.

For multiple commands in a single shell section, Navlang will save their stdout, stderr and status values all in seperate variables, so that you can check them by adding an index number at the end of the names, like this:

    echo 'hello'
    echo 'world'

stdout1 is 'hello'
# in this case `stdout` and `stdout1` are equivalent
stdout2 is 'world'
stderr3 contains /meathill:( command)? not found/
status3 eq '127'

The index number starts from 1. stdout1 is equivalent to stdout, stderr1 is equivalent to stderr, and status1 is equivlent to status.

If a command line ends with \, then this line will be continued to the next line to form a single command for executing. For example:

    echo 'hello \

stdout is 'hello \nworld'
# spaces at the beginning of the next line will be ignored.

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Commands and result output to markdown

If the shell section is surrounded by capture begin/end pair, the commands inside shell section and the output of the commands will be output to the markdown content if --gen-doc is enabled. For example:

capture begin

    echo 'hello'
    echo 'world'

capture end

    Let's use the classic example.

This will generate a markdown file:

$ echo 'hello'
$ echo 'world'

Let's use the classic example.

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Navlang supports the following commands:

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Forcefully set the default language of browser.

lang "en"

goto URL

Goto the URL specified.

click -> ID

Emits a click event to the element of the id ID. For example,

    [Button "Login"]=login

click -> login

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Stops the execution of the navlang program and leaves the web browser as is. When highlight is enabled, the last highlighted elements will display again.


Exits the processing without running any subsequent commands. Unlike the stop command, this quits the web browser and everything.


Prints the value of MESSAGE to stderr. MESSAGE should be quoted and Navlang will treat everything in MESSAGE as a pure string to show.

# Warning: something's wrong at line 1, a.nav.

warn "hello"
# "hello" at line 1, a.nav.

warn "hello\n"
# hello

warn hello world
# invalid argument syntax for "warn"

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Reloads the current web page.

wait network

Waits for the network to be idle.

sleep NUMBER

Sleep for NUMBER seconds. Sometimes we need to wait for an animation to finish playing, then you can use this command.

NUMBER could be an integer or a decimal, like 1, 5, 0.5, 12.5, etc.

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Enters the text STRING into the input element of the id ID. Note that when the element is <select> element, this command can select the <option> which has the label as STRING, not the value attribute of option. If the element is File, this can also be used to select the files by file paths. For example,

    [File "Upload"]=file
"a.html" -> file

To select multiple files, use this:

    [File "Upload"]=file
"a.html", "fileb", "fileC" -> file

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press(KEY) -> ID or press(KEY)

Emits a keyboard event with some special keys. Currently supported keys are Escape, Enter and Delete. Element's ID is optional. If no element is specified, keyboard event will be fired on the window. For example,

    [Textbox "Search..."]=search

"foobar" -> search
press('Enter') -> search

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Checks the state of the element with the id ID.

For Checkbox, Radio and Toggle, they can be checked whether they are checked, or disabled, or readonly.

For Textbox and Dropdown, they can be checked whether they are disabled, or readonly, or required.

For Button, they can be checked whether they are disabled.

All the other elements cannot be checked for any of these states.

For example,

    [Checkbox "check this"]=checkbox
    [Textbox "text here"]=textbox
    [Dropdown "element type"]=dropdown
    [Button "disabled button"]=button
click -> checkbox
checkbox is checked
click -> checkbox
checkbox is unchecked
textbox is readonly
dropdown is required
button is disabled

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ID eq|contains "something"|/something/

Checks the value of the element with the id ID.

For Textbox and Dropdown, it can be checked whether the value is equal to some string or matches a regex (flag not supported), or contains some string.

For example,

    [Textbox "Text"]=textbox
"write something here" -> textbox
textbox eq 'write something here'
textbox eq /write.*here/
textbox contains "write"
textbox contains /some/

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capture begin|end|shot|shot zoomin

Takes a screenshot or make a record for generating a GIF file.

Taking screenshots

For example,

    [Textbox "Text1"]=box1
    [Textbox "Text2"]=box2

capture shot
capture shot zoomin

The frist capture shot command just takes a screenshot of the whole window:

The second capture shot zoomin command would take a screenshot which zooms in to cover the previous elems sections and highlights elements with ID:

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Generating GIF animations

This feature is only available on MacOS. You need to install recording tools by npm install aperture util and install ffmpeg. For example,

capture begin

    [Textbox "Text1"]=box1
    [Textbox "Text2"]=box2

"hello world" -> box1
"live long and prosper" -> box2

capture end

Note that the browser should be headless: false as the recording tool records the video on the real desktop and then converts the video to GIF file. So you need to run it with NAVLANG_SHOW_UI=1. The generated GIF file is like:

For both screenshots and GIF files, if --gen-doc is enabled, the images will be inserted to the markdown content.

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Drags the element with FROM_ELEM_ID and drops on the element with TO_ELEM_ID.

It is implemented by mouse events which can be used to simulate drag. But this can only be used on the website where the drag-and-drop is also implemented by mouse events. If the target site implements the drag-and-drop by HTML standard drag and drop API, this command cannot fire the drop event, it is due to the limitation of puppeteer.

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new|switch|close tab TAB_ID

Defines several browser tabs operations:

  • new tab TAB_ID opens a new browser tab and named it with ID TAB_ID. The ID of the new browser tab cannot be default since it is reserved for the default tab.

  • switch tab TAB_ID activates the browser tab with TAB_ID.

  • close tab TAB_ID closes the browser tab with TAB_ID.

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hover ID

Moves the mouse over the element of the id ID, for example:

    [Button "Login"]=login

hover login

If you want to hover the element for some specific time, you can use sleep command after hover. For example,

    [Button "Login"]=login

hover login
sleep 3
click -> login

Also, next user interactive operation will wait for network idle.

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External Variables

External variables are supported in navlang. The value of the external variables can be specified via command line arguments or the environment variables.

Use $*VARIABLE_NAME to reference an external variable in navalang file. For example, the following is test.nav file:

goto "https://$*TEST_HOST"

# --------- login page ---------

    [Title "Login"]
    [Textbox "User  Name"]=user
    [Textbox "Password"]=pass
    [Checkbox "Remember Me"]=remem
    [Button "Login"]=login

"$*TEST_USER" -> user
"$*TEST_PASS" -> pass
click -> remem
click -> login

To compile the navlang above, we can use command line arguments like this:

./navlang --define \
--define TEST_USER=test-user \
--define TEST_PASS=test-password test.nav

We can also specify them using environment variables like this:

export TEST_USER=test-user
export TEST_PASS=test-password
./navlang test.nav

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