tests: add test cases around empty values

internal/lang/functions_test.go

@@ -323,6 +323,36 @@ func TestFunctions(t *testing.T) {
 				`endswith("hello world", "hello")`,
 				cty.False,
 			},
+			{
+				`endswith("hello world", "")`,
+				cty.True,
+				// Completely empty suffix value  ( "" )
+				// will always evaluate to true for all strings.
+			},
+			{
+				`endswith("hello world", " ")`,
+				cty.False,
+			},
+			{
+				`endswith("", "")`,
+				cty.True,
+			},
+			{
+				`endswith("", " ")`,
+				cty.False,
+			},
+			{
+				`endswith(" ", "")`,
+				cty.True,
+			},
+			{
+				`endswith("", "hello")`,
+				cty.False,
+			},
+			{
+				`endswith(" ", "hello")`,
+				cty.False,
+			},
 		},
 
 		"file": {
@@ -836,6 +866,36 @@ func TestFunctions(t *testing.T) {
 				`startswith("hello world", "world")`,
 				cty.False,
 			},
+			{
+				`startswith("hello world", "")`,
+				cty.True,
+				// Completely empty prefix value  ( "" )
+				// will always evaluate to true for all strings.
+			},
+			{
+				`startswith("hello world", " ")`,
+				cty.False,
+			},
+			{
+				`startswith("", "")`,
+				cty.True,
+			},
+			{
+				`startswith("", " ")`,
+				cty.False,
+			},
+			{
+				`startswith(" ", "")`,
+				cty.True,
+			},
+			{
+				`startswith("", "hello")`,
+				cty.False,
+			},
+			{
+				`startswith(" ", "hello")`,
+				cty.False,
+			},
 		},
 
 		"strrev": {