add some more tests:

Author: d050150

document-readers/pdf-reader/src/main/java/org/springframework/ai/reader/pdf/layout/TextLine.java

@@ -77,8 +77,8 @@ private int computeIndexForCharacter(final Character character) {
 		}
 	}
 
-	private boolean isSpaceCharacterAtIndex(int index) {
-		return this.line[index] == SPACE_CHARACTER;
+	private boolean isNotSpaceCharacterAtIndex(int index) {
+		return this.line[index] != SPACE_CHARACTER;
 	}
 
 	private boolean isNewIndexGreaterThanLastIndex(int index) {
@@ -90,7 +90,7 @@ private int getNextValidIndex(int index, boolean isCharacterPartOfPreviousWord)
 		if (!this.isNewIndexGreaterThanLastIndex(index)) {
 			nextValidIndex = this.lastIndex + 1;
 		}
-		if (!isCharacterPartOfPreviousWord && index > 0 && !this.isSpaceCharacterAtIndex(index - 1)) {
+		if (!isCharacterPartOfPreviousWord && index > 0 && this.isNotSpaceCharacterAtIndex(index - 1)) {
 			nextValidIndex = nextValidIndex + 1;
 		}
 		this.lastIndex = nextValidIndex;

document-readers/pdf-reader/src/test/java/org/springframework/ai/reader/pdf/layout/TextLineTest.java

@@ -8,6 +8,7 @@
 import java.util.stream.Stream;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 
 class TextLineTest {
@@ -88,4 +89,30 @@ void testGetLine() {
 		TextLine textLine = new TextLine(100);
 		assertEquals(" ".repeat(100 / ForkPDFLayoutTextStripper.OUTPUT_SPACE_CHARACTER_WIDTH_IN_PT), textLine.getLine());
 	}
+
+	@Test
+	void testNegativeLineLength() {
+		IllegalArgumentException exception = assertThrows(IllegalArgumentException.class, () -> {
+			new TextLine(-100);
+		});
+		assertEquals("Line length cannot be negative", exception.getMessage());
+	}
+
+	@Test
+	void testComputeIndexForCharacter_CloseToPreviousWord() {
+		TextLine textLine = new TextLine(100);
+		Character character = new Character('A', 10, true, false, true, true);
+		textLine.writeCharacterAtIndex(character);
+		assertEquals(" A" + " ".repeat(23), textLine.getLine());
+	}
+
+	@Test
+	void testComputeIndexForCharacter_CloseToPreviousWord_WriteTwoCharacters() {
+		TextLine textLine = new TextLine(100);
+		Character character = new Character('A', 10, true, false, true, true);
+		Character anotherCharacter = new Character('B', 1, true, false, true, true);
+		textLine.writeCharacterAtIndex(character);
+		textLine.writeCharacterAtIndex(anotherCharacter);
+		assertEquals(" AB" + " ".repeat(22), textLine.getLine());
+	}
 }