---
title: 2. Parsing Test
---


The first test will check if the parser, implemented in the
[Lexer and Parser Definition](/tutorials/custom_language_support/lexer_and_parser_definition.md)
section of the
[Custom Language Support Tutorial](/tutorials/custom_language_support_tutorial.md)
works as we expect it.

### 2.1. Define input test data

Create a file *ParsingTestData.simple* in *testData* folder.

```bash
# You are reading the ".properties" entry.
! The exclamation mark can also mark text as comments.
website = http://en.wikipedia.org/

language = English
# The backslash below tells the application to continue reading
# the value onto the next line.
message = Welcome to \
          Wikipedia!
# Add spaces to the key
key\ with\ spaces = This is the value that could be looked up with the key "key with spaces".
# Unicode
tab : \u0009
```

### 2.2. Copy the expected PSI tree

The easiest way to get the expected PSI structure for any file is to use PSI Viewer.
Run the project and call `Tools` → `View PSI Structure`.

![PSI Tree Copy](img/plugin_copy_psi.png)

Use `Copy PSI` button to copy the expected PSI structure to the clipboard.

### 2.3. Define an output test data

Create a file *ParsingTestData.txt* with the copied PSI tree.

```java
Simple File(0,433)
  PsiComment(SimpleTokenType.COMMENT)('# You are reading the ".properties" entry.')(0,42)
  PsiElement(SimpleTokenType.CRLF)('\n')(42,43)
  PsiComment(SimpleTokenType.COMMENT)('! The exclamation mark can also mark text as comments.')(43,97)
  PsiElement(SimpleTokenType.CRLF)('\n')(97,98)
  SimplePropertyImpl(PROPERTY)(98,132)
    PsiElement(SimpleTokenType.KEY)('website')(98,105)
    PsiWhiteSpace(' ')(105,106)
    PsiElement(SimpleTokenType.SEPARATOR)('=')(106,107)
    PsiWhiteSpace(' ')(107,108)
    PsiElement(SimpleTokenType.VALUE)('http://en.wikipedia.org/')(108,132)
  PsiElement(SimpleTokenType.CRLF)('\n')(132,133)
  PsiElement(SimpleTokenType.CRLF)('\n')(133,134)
  SimplePropertyImpl(PROPERTY)(134,152)
    PsiElement(SimpleTokenType.KEY)('language')(134,142)
    PsiWhiteSpace(' ')(142,143)
    PsiElement(SimpleTokenType.SEPARATOR)('=')(143,144)
    PsiWhiteSpace(' ')(144,145)
    PsiElement(SimpleTokenType.VALUE)('English')(145,152)
  PsiElement(SimpleTokenType.CRLF)('\n')(152,153)
  PsiComment(SimpleTokenType.COMMENT)('# The backslash below tells the application to continue reading')(153,216)
  PsiElement(SimpleTokenType.CRLF)('\n')(216,217)
  PsiComment(SimpleTokenType.COMMENT)('# the value onto the next line.')(217,248)
  PsiElement(SimpleTokenType.CRLF)('\n')(248,249)
  SimplePropertyImpl(PROPERTY)(249,292)
    PsiElement(SimpleTokenType.KEY)('message')(249,256)
    PsiWhiteSpace(' ')(256,257)
    PsiElement(SimpleTokenType.SEPARATOR)('=')(257,258)
    PsiWhiteSpace(' ')(258,259)
    PsiElement(SimpleTokenType.VALUE)('Welcome to \\n          Wikipedia!')(259,292)
  PsiElement(SimpleTokenType.CRLF)('\n')(292,293)
  PsiComment(SimpleTokenType.COMMENT)('# Add spaces to the key')(293,316)
  PsiElement(SimpleTokenType.CRLF)('\n')(316,317)
  SimplePropertyImpl(PROPERTY)(317,410)
    PsiElement(SimpleTokenType.KEY)('key\ with\ spaces')(317,334)
    PsiWhiteSpace(' ')(334,335)
    PsiElement(SimpleTokenType.SEPARATOR)('=')(335,336)
    PsiWhiteSpace(' ')(336,337)
    PsiElement(SimpleTokenType.VALUE)('This is the value that could be looked up with the key "key with spaces".')(337,410)
  PsiElement(SimpleTokenType.CRLF)('\n')(410,411)
  PsiComment(SimpleTokenType.COMMENT)('# Unicode')(411,420)
  PsiElement(SimpleTokenType.CRLF)('\n')(420,421)
  SimplePropertyImpl(PROPERTY)(421,433)
    PsiElement(SimpleTokenType.KEY)('tab')(421,424)
    PsiWhiteSpace(' ')(424,425)
    PsiElement(SimpleTokenType.SEPARATOR)(':')(425,426)
    PsiWhiteSpace(' ')(426,427)
    PsiElement(SimpleTokenType.VALUE)('\u0009')(427,433)
```

### 2.4. Define a parsing test

```java
{% include /code_samples/simple_language_plugin/tests/com/simpleplugin/SimpleParsingTest.java %}
```

### 2.5. Run the test

Run the test and make sure it's green.