Added test class for DummyWarning (#810)

* Added test class for DummyWarning
### What's done:
* Added test class for DummyWarning, which shows the general form of how to test your rule
* Add newline in guide-chapter-1, since table wasn't displayed

diktat-rules/src/test/kotlin/org/cqfn/diktat/ruleset/dummy/DummyWarningWarnTest.kt

@@ -0,0 +1,31 @@
+package org.cqfn.diktat.ruleset.dummy
+
+import org.cqfn.diktat.ruleset.constants.Warnings.DUMMY_TEST_WARNING
+import org.cqfn.diktat.ruleset.rules.DIKTAT_RULE_SET_ID
+import org.cqfn.diktat.util.LintTestBase
+
+import com.pinterest.ktlint.core.LintError
+import generated.WarningNames
+import org.junit.jupiter.api.Disabled
+import org.junit.jupiter.api.Tag
+import org.junit.jupiter.api.Test
+
+/**
+ * In this class you can test the logic of your rule, which should be implemented in DummyWarning
+ */
+class DummyWarningWarnTest : LintTestBase(::DummyWarning) {
+    private val ruleId = "$DIKTAT_RULE_SET_ID:dummy-rule"
+
+    // Remove @Disabled annotation before usage
+    @Disabled
+    @Test
+    @Tag(WarningNames.DUMMY_TEST_WARNING)
+    fun `check dummy property`() {
+        lintMethod(
+            """
+                |// provide your check here
+            """.trimMargin(),
+            LintError(1, 1, ruleId, "${DUMMY_TEST_WARNING.warnText()} some detailed explanation", true)
+        )
+    }
+}

info/guide/guide-chapter-1.md

@@ -40,6 +40,7 @@ The only exception is function names in `Unit tests.`
  @Test fun `my test`() { /*...*/ }
 ``` 
 6.  The following table contains some characters that may cause confusion. Be careful when using them as identifiers. To avoid issues, use other names instead.
+
 | Expected      | Confusing name           | Suggested name   |
 | ------------- | ------------------------ | ---------------- |
 | 0 (zero)      | O, D                     | obj, dgt         |