Unit tests for StringBuilderUtils, fixing trim method in StringBuilderUtils

app/src/main/java/acr/browser/lightning/utils/StringBuilderUtils.java

@@ -14,8 +14,8 @@ public class StringBuilderUtils {
     private static final String EMPTY = "";
 
     /**
-     * Replace a string in a string
-     * builder with another string.
+     * Replace the first string found in a
+     * string builder with another string.
      *
      * @param stringBuilder the string builder.
      * @param toReplace     the string to replace.
@@ -42,7 +42,7 @@ public class StringBuilderUtils {
             stringBuilder.replace(0, 1, EMPTY);
         }
 
-        while (stringBuilder.lastIndexOf(SPACE) == (stringBuilder.length() - 1)) {
+        while (stringBuilder.lastIndexOf(SPACE) == (stringBuilder.length() - 1) && stringBuilder.length() > 0) {
             stringBuilder.replace(stringBuilder.length() - 1, stringBuilder.length(), EMPTY);
         }
     }

app/src/test/java/acr/browser/lightning/utils/StringBuilderUtilsTest.java

@@ -0,0 +1,118 @@
+package acr.browser.lightning.utils;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * Tests for {@link StringBuilderUtils}.
+ */
+public class StringBuilderUtilsTest {
+
+    @Test
+    public void replace_SingleCharacter() {
+        StringBuilder stringBuilder = new StringBuilder("abbbaacccda");
+        StringBuilderUtils.replace(stringBuilder, "a", "");
+        Assert.assertEquals(stringBuilder.toString(), "bbbaacccda");
+    }
+
+    @Test
+    public void replace_MultipleCharacters() {
+        StringBuilder stringBuilder = new StringBuilder("___ab___cd___");
+        StringBuilderUtils.replace(stringBuilder, "___", "---");
+        Assert.assertEquals(stringBuilder.toString(), "---ab___cd___");
+    }
+
+    @Test
+    public void trim_LeadingAndTrailingSpaces() {
+        StringBuilder stringBuilder = new StringBuilder(" t e s t        ");
+        StringBuilderUtils.trim(stringBuilder);
+        Assert.assertEquals(stringBuilder.toString(), "t e s t");
+    }
+
+    @Test
+    public void trim_OnlyContainsSpaces() {
+        StringBuilder stringBuilder = new StringBuilder("           ");
+        Assert.assertFalse(stringBuilder.toString().isEmpty());
+        StringBuilderUtils.trim(stringBuilder);
+        Assert.assertTrue(stringBuilder.toString().isEmpty());
+    }
+
+    @Test
+    public void isEmpty_HasNoCharacters() {
+        StringBuilder stringBuilder = new StringBuilder("");
+        Assert.assertTrue(StringBuilderUtils.isEmpty(stringBuilder));
+    }
+
+    @Test
+    public void isEmpty_HasCharacters() {
+        // Case with normal letters
+        StringBuilder stringBuilder = new StringBuilder("abcdefg");
+        Assert.assertFalse(StringBuilderUtils.isEmpty(stringBuilder));
+
+        // Case with empty spaces
+        StringBuilder stringBuilder1 = new StringBuilder("       ");
+        Assert.assertFalse(StringBuilderUtils.isEmpty(stringBuilder1));
+    }
+
+    @Test
+    public void startsWith_SingleCharacter() {
+        StringBuilder stringBuilder = new StringBuilder("1234567890");
+        Assert.assertTrue(StringBuilderUtils.startsWith(stringBuilder, "1"));
+        Assert.assertFalse(StringBuilderUtils.startsWith(stringBuilder, "2"));
+    }
+
+    @Test
+    public void startsWith_MultipleCharacters() {
+        StringBuilder stringBuilder = new StringBuilder("1234567890");
+        Assert.assertTrue(StringBuilderUtils.startsWith(stringBuilder, "12345"));
+        Assert.assertFalse(StringBuilderUtils.startsWith(stringBuilder, "23456"));
+    }
+
+    @Test
+    public void contains_SingleCharacter() {
+        StringBuilder stringBuilder = new StringBuilder("abcdefg123456");
+
+        // This character is not in the string
+        Assert.assertFalse(StringBuilderUtils.contains(stringBuilder, "z"));
+
+        // All these characters are in the string
+        for (int n = 0; n < stringBuilder.length(); n++) {
+            Assert.assertTrue(StringBuilderUtils.contains(stringBuilder, String.valueOf(stringBuilder.charAt(n))));
+        }
+    }
+
+    @Test
+    public void contains_MultipleCharacters() {
+        StringBuilder stringBuilder = new StringBuilder("abcdefg123456");
+
+        // Should return false since characters are in reverse order
+        Assert.assertFalse(StringBuilderUtils.contains(stringBuilder, "cba"));
+
+        // Should return false since characters are not in string
+        Assert.assertFalse(StringBuilderUtils.contains(stringBuilder, "zyx"));
+    }
+
+    @Test
+    public void equals_SameCharacters() {
+        StringBuilder stringBuilder = new StringBuilder("abcdefg");
+
+        Assert.assertTrue(StringBuilderUtils.equals(stringBuilder, "abcdefg"));
+    }
+
+    @Test
+    public void equals_DifferentCharacters() {
+        StringBuilder stringBuilder = new StringBuilder("abcdefg");
+
+        Assert.assertFalse(StringBuilderUtils.equals(stringBuilder, "abcdefg1"));
+    }
+
+    @Test
+    public void substring() {
+        StringBuilder stringBuilder = new StringBuilder("abcdefg");
+
+        String string = "abcdefg";
+
+        Assert.assertEquals(StringBuilderUtils.substring(stringBuilder, 1, 5).toString(), string.substring(1, 5));
+    }
+
+}