test:add test case for StringFormatUtils (#3579)

common/src/test/java/io/seata/common/util/StringFormatUtilsTest.java

+package io.seata.common.util;
+
+import org.junit.jupiter.api.Test;
+import static org.assertj.core.api.Assertions.assertThat;
+
+class StringFormatUtilsTest {
+
+    @Test
+    void camelToUnderline() {
+        assertThat(StringFormatUtils.camelToUnderline(null)).isEqualTo("");
+        assertThat(StringFormatUtils.camelToUnderline("  ")).isEqualTo("");
+        assertThat(StringFormatUtils.camelToUnderline("abcDefGh")).isEqualTo("abc_def_gh");
+    }
+
+    @Test
+    void underlineToCamel() {
+        assertThat(StringFormatUtils.underlineToCamel(null)).isEqualTo("");
+        assertThat(StringFormatUtils.underlineToCamel("  ")).isEqualTo("");
+        assertThat(StringFormatUtils.underlineToCamel("abc_def_gh")).isEqualTo("abcDefGh");
+    }
+
+    @Test
+    void minusToCamel() {
+        assertThat(StringFormatUtils.minusToCamel(null)).isEqualTo("");
+        assertThat(StringFormatUtils.minusToCamel("  ")).isEqualTo("");
+        assertThat(StringFormatUtils.minusToCamel("abc-def-gh")).isEqualTo("abcDefGh");
+    }
+
+    @Test
+    void dotToCamel() {
+        assertThat(StringFormatUtils.dotToCamel(null)).isEqualTo("");
+        assertThat(StringFormatUtils.dotToCamel("  ")).isEqualTo("");
+        assertThat(StringFormatUtils.dotToCamel("abc.def.gh")).isEqualTo("abcDefGh");
+    }
+}
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